I'd try a few in an area I knew that the carp fed to find out if they would eat them. If not I'd be using them to feed the swans to keep them off my bait.
A mate of mine opened this place last year:
Home | Fieldview Fishery
Not been yet myself but it gets rave reviews and has a very plush lodge. The owner is an absolute diamond so more than happy to vouch for the place.