We offer a wide and diverse wealth of experience within the Sunningdale practice, which is also reflected in the width and diversity of our client portfolio from owner managed businesses and private clients to professional practices and large international groups.

With 70 years’ expertise in UK and international markets we offer clients dependable and best advice throughout their business and personal financial lives.

We are genuinely client focused and put the needs of our clients first. Ongoing appraisals ensure we offer advice and assistance when it’s required.


Dawn O'Leary


For audit & assurance, accountancy and international business services

Graduated from Dundee University with an MA (Hons) in Accountancy and qualified as a Chartered Accountant in 1992 with a top 50 firm in Scotland before moving south. Dawn has been with Davis Burton Sellek in Sunningdale Ascot since. In 1998 she was admitted as a partner and is now the firm's Managing Partner.

Dawn has developed a mixed and diverse client portfolio comprising small, medium and large companies in market areas including construction, shipping, recruitment and property. Her local client base covers Berkshire. Surrey, Hampshire and London. She also has an increasing number of national and international clients including Dutch, Hungarian, Austrian, German, Turkish, Indian, American and Far Eastern. One specific area of expertise is advising overseas companies operating on large UK projects.

Responsible for audit, accountancy and business services, Dawn ensures that all clients have a dedicated manager and team suited to their specific requirements. She is passionate about the role which small to medium sized businesses play in today's market and how the accountancy profession can best serve their needs.

She is governor for a local independent girls' school and recently sat on the General Practitioners Committee of the Institute of Chartered Accountants of Scotland (ICAS) representing members in England and Wales. She continues to be involved in ICAS working party groups addressing those issues crucial to the profession and business generally.

Get in touch with Dawn at:


Mark Busby


For personal and corporate tax advice specialising in Non-Domiciles and Expatriates

Having been trained by the Inland Revenue and after serving with them for five years Mark moved into private practice where he obtained his professional qualifications and became a member of The Association of Taxation Technicians. He was admitted as Tax Partner with Davis Burton Sellek Sunningdale Ascot in 2010.

With over 20 years' experience he advises on both business and personal tax matters, specialising in international tax issues, complex high net worth tax advice and wealth planning. His enviable reputation in the local and international arena extends to representing clients across a range of sectors including Trusts, Lloyds Underwriters and Non UK domiciliaries. His experience in advising on personal and corporate taxation extends across the US, South African, European, Indian and Turkish markets.

As the firm’s Tax Partner Mark aims to provide a “Boutique" service tailored around individual needs and believes strongly that good tax advice comes from getting to know clients, their backgrounds and the issues that affect their lives before even discussing the numbers.

Get in touch with Mark at: