Hello Phred and welcome to the forum! In your price
range (and with your intended use and the beam restriction in the canals), I would recommend the Solaris Sunrise 36. While they are not known as fast sailors, they were well built, very comodious, typically fit with inboard diesel power
and had a BOA of 4.82 meters.
You could also consider a used Gemini
3200 or 3400, although most were fitted with outboards rather than diesels. These are still comodious and while not as solidly built as the Sunrise 36, they were much faster on all points of sail (albiet availability in the UK/Europe may be limited).
Finally, various Prouts and Catalacs in your price
range will also meet your beam limitations and will have comparable construction quality to the Solaris (and sadly, comparable performance limitations, especially if heavily loaded for cruising).
Cheers and happy cat hunting!