6.85m is perfectly capable of crossing channel etc. Many smaller boats do so, as ever its a question of picking your conditions, but since you've been ribbing for so long you'll be up on that anyway!
6.85 & 200hp should go like stink I'dve thought
Yam Hpdi is a cracking engine, I have one on my Scorpion. You should get around a litre per mile at cruising speed - 25-35kts.
Insurance - "standard" cover is usually upto 30m offshore but ask for "Brest to Elbe" cover which covers you for cross channel, North Sea, Irish sea etc. Shouldn't cost much if any more. I use Mardon who have been ok for insurance. I'm sure this has been discussed before here so try a search for insurance.
Cruising in company is always a sensible move, particularly for the longer trips. Cruises get organised here - e.g. Channel Islands, Rib.net gathering & Orkney SIB challenge. You could also consider joining BIBOA - British RIB Club who organise cruising and racing events throughout the year. Email firstname.lastname@example.org