will the M5 imac be in store before Christmas in uk?

Apple has not announced if, or when, there will be a 24" M5 iMac. It seems likely that there will eventually be one – but note that there was no 24" M2 iMac – they kept the 24" M1 iMac around until the 24" M3 iMac was ready to go.

The people on this forum are mostly other users who do not know when new iMacs are coming out. Some predictions are easy to make based on the historical record (e.g., Apple is almost certain to release a new version of macOS, next year, in the fall), but others get into speculative areas, and Apple frowns on speculation here.

If there are any Apple employees who happen to be reading these forums and who know the answer, those people would likely be bound by NDAs ("I could tell you, but then I'd have to kill you.").

There has been no M5 iMac announced, so it's impossible to know when it will be available, much less if it will happen before Christmas.

Assume it won't be.

With that said, the M4 iMac was released lats year around the first week of November, so maybe, but not known at this time whether it will be or not.