Sea Ray 315's don't seem to be available with twin diesels but a single pushes it along well. Prior to the Fairline I had a Sea Ray 260 which for its size was good in the chop on south coast.
Other thing to consider is what you want from the interior. UK boats will have a separate cabin, the US boats will be open plan.
Suggest you having a look about about US/UK models. You'll get a newer US boat.
On the basis of your checklist, a UK boat (or at least a non US boat) is more likely to fit the bill, esp. the twin engine and side decks requirements
OK, 30' twin diesel, mostly day boat, 2000-2007, £70 k budget, that's a fair spec. You know about the UK options, so are asking for info about other possibilities.
You may just get a Windy Tornado 31 for that, but will be at the oldest end of your range. There's a 1997 available at £70k, which you'd probably get for £60k. These are fast, sleek, and well built, but lack accommodation, and have an unusual, but very useable, cockpit layout.
Next a Cranchi Giada 30, slower, fatter, but more accomodation. A 2002 in Southampton asking £60k. Also from Italy, a Sessa Oyster 30, or Gobbi 315. Again, they're more cruising boats than the Windy, with more space. They're thin on the ground in the UK, but if you can find one you should be able to get a quite late model for your budget.
In the very unlikely event that you want a big sunpad, but little in the way of cockpit seating, then look at a Cranchi Endurance 33. I think Abersoch Land and Sea managed to flog a few of these even though they're far from ideal for UK boating, especially in N Wales. As a result they sell for peanuts second hand, for the size and quality of boat. Don't do it unless you're really sure you want that cockpit layout though, it's a med boat through and through.
Bavaria has already been mentioned, built to a price but owners seem happy with them.
I'll let someone else run through the N American options, as I don't know them that well, other than to say I was v pleased with my 2 Chaparrals.