Which country in Britain are you from? That may determine possible suggestions.
For example, a quaich is a traditional wedding gift in Scotland and we have taken this abroad for several weddings and it has been very well received, but we are Scottish - if you are English or Welsh, it may not be as relevant.
Another suggestion is a woollen or tweed blanket or throw, but depends on your budget as they are likely to be very expensive.
A Welsh love spoon is a beautifully carved wooden spoon, which would transport easily and you can get them personalised, which would be a nice touch.
If you are English, maybe a pewter horseshoe?
How about some mugs - if they are gift boxed, they would travel ok, or you could keep them in your hand luggage. Harrods or Fortnum and Mason might be worth considering?
Or Emma Bridgewater Mr & Mrs mugs?They also do a Mr & Mrs gift tin that you could put in some English tea, shortbread etc?