Hi Chris,
I work at a seal sanctuary so can offer a bit of advice. The Grey seal breeding season is coming to an end for this year (Sept-March) so it's unlikely you're going to get them hauled out in great numbers right now. In good old Kernow the first pups are usually born late September, and the months leading up to Christmas are usually the best for finding them. The Common seal breeding season will be in the summer months and so they are the next to be coming on to the beaches in numbers. They are primarily found on the eastern coast of England and Scotland. Quite rare to find them on the western coast any time of year.
During breeding season the seals will be on the beaches for most of the day, out of season they spend the majority of time in deeper water feeding and only coming back to land to sleep (though they can sleep in water if need be).
A couple words of warning though, please don't attempt to approach seals in water or on the beach. They can be very aggressive towards humans and have a nasty bite with a very high infection risk; or at the very least you will scare them off the beach where they are trying to rest and digest food. If you were to approach a pup the mother will simply abandon it and the pup will die without regular feeds from her.
Whatever you do, please never feed a wild seal!!! There are numerous reasons why but two of the biggest are that most people would feed seals over the tourist seasons, then out of seasons the seals will approach boats to find food rather than hunt for themselves. The other possibility is that the seals will approach fishing vessels which are licensed to shoot them. Feeding a wild seal may lead it to getting shot - not a nice turn of events.
If you do find a seal that looks like it's in trouble then please contact the British Divers Marine Life Rescue hotline: 01825 765546
If you have any other questions feel free to ask!