who knows how to properly margin calendar spreads. I heard back from a couple but at $10 per contract per side it seemed steep, I am based in UK.
You mean properly margin, or charge lower commissions?
I'm UK based, and use IB. Margin for calendars seems to be okay-ish, but I don't usually check that against the official SPAN figures. I also use DeCarley as a broker, who charge a higher commission, but are good with selling naked options on futures (IB apply a VERY high margin for that).