...a 25 tyre leaves it very hard to get wheel on.
Jags, if the problem with wider tires is getting them past the brake pads (usually a problem when using wider tires with the brakes adjusted for narrower rims), just insert the wheels with the tires uninflated, then air 'em up once in place.
If the problem is lack of clearance with the chainstays, fork crown or mudguards, then that solution won't work, of course.
Best,
Dan. (...who has to do this on several of his own 700C-wheeled bikes)