There’s a local model engineering club running trains on Sunday for testing, no rides. I expect that will mean very few, if any, members of the public present. The club have said I’m ok to fly but I want to be sure.
Public excepted, the site is drone code friendly. I can even stand more than 50 metres away from their own building.
With it being private and with their permission, am I OK to fly even if there’s other non-members of the club like me present?
Based on what you’ve said here, I see no reason why not.
As long as you tell them what’s going on then the building and club members can be deemed to be in your control so no need to worry about 50m
Just check the air space with Drone Scene or the NATS drone assist phone app for any restrictions, if non then you’re good to fly. You already have the land owners permission to take off, land and operate your drone from their land so all good 
No restrictions anywhere near, roads & West coast mainline far enough away. However, it’s a public picnic site in the middle of the circuit but I’m lucky because our council’s drone rules are follow the drone code. No rides today so the only non-members are walkers parking up & heading off.
As always though, the wind forecast was wrong and the Mini needs to stay low 
50m bubble from the picnic area so all good. 
hope the wind stays slow enough for you to fly the mini can handle some wind just make sure you’re flying out into the wind so you have the wind at your back when you’re returning home
Hi Doodler where did you find Lancashire / Cumbria councils drone rules? Struggling to find them online.
I emailed Lancaster City Council, not county, and they replied with that info.
Cheers doodler ill send them an email too, print out their response and put in my uav bag. 
It’s the sort of email worth saving. Hate to say I can’t find it, or can’t find the correct keywords to find it.