Thanks guys I was installing stuff only just seen your replies.

Well I settled with the 5" fan, filter & duct kit.

Im up a few stories, no worries about smell outside so I dont mind really if smells go out.. the roof is above me.. not even a flat accessible one. I just
cant have the smell in the house.

The wiring, mains, it gos up to the top closet for the fan and ballast. Ive covered the room now with light proof flame resistant mylar. Floor with waterproofing plastic. Sealed the door edges pretty well with draft excluder, could be done a touch more but the doors are awkward.

When the fan is running air is being sucked in via the 4" hole at the bottom near the window... it starts sucking from a good foot distance. Padded the fan out with cushions... my ballast is the nosiest cause of its fan but thats all fine and hushed enough.

Lights are on a relay of course.

I can have it running all day and the temps are pretty cool even if the lamp does get hotter than I hoped it would I can still touch it for a long while. I am venting from quite a distance and a few bends though.. so it would be even better with an intake fan bringing in cool air.

I'l attach some photos.. I looked around at other setups and note the filter goes at the top yeah, this is the only position I can fit it in there [as others Ive seen] it can go depth ways but the ducting dont fit.

Ive tested this setup by spraying the bottom of the closet with a bit of air freshener then smelling the vent out..... and I can smell the air freshener so now what do I do?

I have been reading endless debates on suck or pull through the vent.. and I come to the conclusion you are supposed to pull it.

Ive also read that maybe high fan speeds are the culprit [to others issues] cause its not giving the filter time.. but what do you think about mine at these distances with bends and 5" RVK? cant be too fast can it?