John Willett said:
For travelling abroad (which I do often) I bought a set of headlight protectors and put the headlight converters on those.
So I just clip them on and off and don't have to keep cleaning sticky of the headlights and then putting new ones on every time.
As an addendum - I changed the bulbs for the extreme bright ones (Philips won the Auto Express test, but I got Halfords ones at two for the price of one).
These give better brightness in the UK and, most important, compensate for the loss in light due to the continental adaptors when driving abroad.
When abroad I always found the lights too dim until I got the extra bright ones.