UX strategy & design leadership
Senior direction, a design operating model, or a partner to raise the bar of an in-house team.
Where strategy meets experience
Full-lifecycle UX, carried end to end by one senior partner.
Research, strategy, design and design systems, from the first question to the shipped product.
Writing, ideas & frameworks
What the work produced
94%
All-time-high satisfaction across a telecom's web touchpoints
40%
Fewer overdue payments after a billing & self-service redesign
5M+
Accounts on a national digital-identity platform
Client names are covered by non-disclosure agreements. Full context on the Work page.
Trusted across industries
Matthaios has led UX work across seven sectors. Most client names are covered by non-disclosure agreements.
Telecom
Retail & e-commerce
Media & TV
Insurance
Public sector
Publishing
Higher education
Services
The full UX discipline, one senior lead
Five UX services, then the specialist services. Matthaios Mantzios leads every engagement himself, and we take on a limited number at a time.
Research & usability testing
Interviews, usability testing and behavioural analysis, turned into design decisions you can defend.
Product & interface design
Information architecture, wireframes and production-ready interfaces your engineers can build with confidence.
Design systems
Component libraries, design tokens and the governance that keeps a system in use.
UX audits
An expert evaluation of your product, with prioritised, effort-ranked recommendations.
AI oversight testing
Whether the people who check an AI system's outputs actually catch its errors. Fixed scope, fixed price.
Accessibility & EAA
WCAG 2.2 and European Accessibility Act audits, from a free checklist to a fixed-price Exposure Report.
Selected work
Senior UX, measurable outcomes
Telecom · Digital identity
One login across a telecom group's websites and apps
Product vision for an identity platform that grew past 5M+ user accounts.
Telecom · Brand merge
Merging two brands into one digital experience
A research-led merge across every digital interface: web-touchpoint satisfaction at an all-time high of 94%.
Self-service · Billing
Billing and self-service for a telecom operator
Call-centre data set what to fix: 90% satisfaction with online payment, overdue payments down 40%.
Resources
Frameworks, tools and reading
Room to Disagree
An open framework for designing and testing the interfaces through which people oversee AI systems.
The iceberg diagrams
What a review usually misses in UX, design systems and accessibility.
The oversight checklist
Twenty yes/no checks for any screen where a person reviews AI output.
Web and Mobile Accessibility
The second edition of the guide to WCAG 2.2, the ADA and the European Accessibility Act.
FAQ
Frequently asked questions
What is UXellence?
UXellence is the UX consultancy of Matthaios Mantzios, a UX design leader with 18+ years of experience. It provides full-lifecycle UX services — strategy, research, product and interface design, design systems and accessibility — for organizations that need senior expertise across the entire product lifecycle.
What UX services does UXellence offer?
UXellence offers UX strategy and design leadership, research and usability testing, product and interface design (including information architecture), design systems and UX audits, plus AI oversight testing and accessibility consulting (WCAG and European Accessibility Act readiness).
Who is Matthaios Mantzios?
Matthaios Mantzios is the founder of UXellence and a UX design leader with over 18 years of experience across telecom, retail and e-commerce, media and TV, insurance, public sector, publishing and higher education. He is Nielsen Norman Group (NN/g) UX certified, a Certified Scrum Product Owner, and the author of Web and Mobile Accessibility: A Comprehensive Guide to WCAG 2.2, the ADA, and the European Accessibility Act (2nd edition).
Does UXellence help with the European Accessibility Act (EAA)?
Yes. UXellence provides WCAG audits and European Accessibility Act readiness roadmaps, led by the author of a comprehensive accessibility guide — including barrier identification, remediation planning and team training.
How do I find out where we stand?
Three ways, by how much certainty you need. The free EAA & WCAG readiness checklist is a 10-minute self-assessment. The EAA Exposure Report is a fixed-scope assessment of ten screens in five working days. A full audit covers the whole product. The Report's fee comes off the audit if you go on to book one.
Do you help Greek public bodies with the AI Registry declaration?
Yes. Under Article 21 of Law 5321/2026, Greek public-sector bodies must declare the AI systems they use, or plan to use, in the national AI Registry; systems in use before the law took effect on 20 July 2026 must be declared by 31 December 2026. UXellence publishes a free guide in Greek and offers fixed-price support for preparing the declaration and testing that human oversight of the system works.
Where is UXellence based?
UXellence is based in Athens, Greece, and works with clients internationally on a remote-first basis.
How do I start a project with UXellence?
Contact UXellence at matthaios@uxellence.gr or through the contact form. Most engagements begin with a short discovery call to scope the right first step — often a UX audit or a focused research sprint.
Work with a senior UX partner, from first insight to launch.
Tell us about your product and the problem you're solving. You'll get a candid view of where senior UX moves the needle — and where it doesn't.
Start a project