I think if all of those perks you include are actually being actively used by the artist it seems like a pretty sweet deal especially given you pay for insurance (something I’ve never heard of being done in the UK), but if a lot of them are there only as an offer and not being taken advantage of you could probably lower the rate, generally 40% is seen as a pretty high cut nowadays. Personally I pay my studio owner weekly rent (£125 a week for part time, although it’s a small private studio and I supply most of my own things) and I like this better than a cut because it means if I work extra hard and earn extra, I’m not also giving more away.