Alasdair Taylor's Answer

In the first instance I suggest writing politely to the person concerned, pointing out the possibility of confusion, and asking whether they would consider using a different domain and/or business name.

If that doesn’t work, legal avenues you could consider include: (i) a domain name arbitration (as this is a .uk domain, that would be using the Nominet procedure, https://www.nominet.uk/domains/resolving-uk-domain-disputes-and-complaints/); and/or (ii) a complaint of passing off (https://en.wikipedia.org/wiki/Passing_off). Domain name arbitration is cheaper, quicker and much less risky than passing off litigation. You should take proper legal advice before going down either route.

NB I am assuming you do not hold a relevant registered trade mark.  If you do, that could help with a domain name arbitration and ground a separate infringement action.