Look at lots of places and work out what style you like.
Hatton garden is good for research as there are so many jewellers.
If you want something a bit less standard/traditional try dinner like Spectrum on south molton street, they have gorgeous art piece jewelry (that's where I got mine).
Or if you want to go to a jeweller and buy from a real crafts-person try local studio groups such as:
401 1/2 studios on Wandsworth Road
http://401studios.org
(I'm a sculptor and I used to have a studio there, there are some amazing jewellers, Gerlind, Heather, Andrew...)
Or
Cockpit Arts
http://cockpitarts.com
Congrats and enjoy
Bx