As far as I know the nearest Honda service dealer would be in Reading
http://www.honda.co.uk/marine/dealers/DLM100.html
No idea if any good, but 20hr first services are really just oil changes to get the crap out etc. to preserve warranty and should be a fixed rate.
If you’ve only done 2 hrs is it worth having it serviced now?
Might be worth asking Honda if it could be serviced say Spring next year when you may have nearer to 20hrs on it. Some manufacturers accept the sporadic seasonal useage outboards get, and can be flexible with the first service time scale, whilst still keeping warranty intact. We had a Suzuki, purchased in October, and serviced in April at 20 odd hrs. The servicing dealer cleared this with Suzuki re warranty.
Also, our current Mariner was registered in December and also serviced following April at 29hrs with no detrimental affect on warranty.