Try Dickies of Bangor - I was quoted £2930 plus delivery inc VAT for the raw water cooled version including loan of the fitting jig. Guy to speak to is Brian Pumfrey on 01248 352 775. Best I could get elsewhere was several hundred pounds more.
He was recommended to me by Dick Stagg of A E Barrus, just before he retired and I've found him a godsend for parts, advice and advice.
An alternative is:
John Skues
Cellar Garage Marine
Penhallow
Helston
Tel 01326 280214
He frequently has re-cons available and, as he services the professional rather than the leisure market knows more and is more in touch with economic reality then the majority of suppliers.