Well I know its a bit out of your way but maybe of some use to others, This guy does a full service for less than 200 with plugs, gear oil, filter, and full diagnostic engine history print out, And he's Evinrude approved as "they" can be fussy who service there outboards.
John Griffiths outboards, Pembrokeshire.
07817 598539,
Hope this is of some use to someone,
I find he's very good and fare.