Leemind,
is it a breach of Rule 5 if you land at a hotel (or similar) within 500' of another helicopter??
Nope. Rule 5 doesn't apply when landing or taking off 'in accordance with normal aviation practice.'
For helicopters, landing at a hotel (as long as you have the landowners permission) is 'in accordance with normal aviation practice'. Now, if you were trying to land a Cessna at the hotel, then the CAA might argue that this isn't 'in accordance with normal aviation practice'...!
Hope this helps,
B73