Beware the HSE too, even if you are allowed to land legally, it being a "public" space I would have expected you to need some sort of written safety assessment agreed with the venue which covers things like small children running out while your rotors are running, action in the event of..... etc. It may also be prudent to let the local police know, assuming it's not a regular occurrence at the venue, or you may end up with someone dialing 999 resulting in a mass response for a crashed heli
Just my 10 peneth having never flown rotary