I think you always initially think a box of chocolates or flowers is a nice gesture, but I think personally if I were on the other end of a thank you present a dinner for 2 at a nice restaurant is a far nicer gift.
….. Or along similar lines but a bit more unique, something my partner and I have recently really enjoyed, is afternoon tea at any of the well known london Hotels ….. we have been to a few over the past few years and The Dorchester is by the far the most impressive.
020 7924 2285
20 Lombard Road
Battersea SW11 3RU