Looks like this was the culprit of my leaky calliper....
One new seal later, at a massive cost of £2.90, and it looks to be working fine. Only got old temp pads in for a few days to see if it stays leak free, then will buy new pads for both front wheels I think.
The cars spent most of today beached at the top of the driveway.
I set about chopping up my exhaust even more. I'm sick of it knocking against the axel, which make it sound like the whole back end of the car is loose. Took me all morning, with various stages of test fitting, but now I've got looooads of clearance. Could drop the car another 4" and still not hit it.
I then set about giving most of the mechanicals a good spraying of ACF50. ACF50 is an anti-corrosion spray, developed for US army for use on tanks. I first heard of it from the Ducati owners and having used it on my own bikes riding through the winter and coming out the otherside with no hint of corrosion I'm confident it will help stop nature from undoing all my restoration work over the coming winter.
I also took the opportunity to polish my wheels. Didn't bother cleaning the rest of the car though, got too impatient to go for a test drive with new exhaust.
As darkness fell I retreated to the garage to make a start on my steering wheel project. I really like the original s2 spec wheel, but I wanted a slightly smaller wheel with a bit more dish. I bought a spare s2 wheel a couple of weeks back and today I cut the rubber off it, then reduced the diameter from 370mm to 330mm and then after plenty of measuring reattached the spokes giving it about 40-50mm of dish.
With the old rubber roughly in pace I'm happy its gonna be just what I wanted. Just gotta get it properly re-covered now.
Last but not least my intake manifold arrived. I get paid Monday and will be ordering my Megasquirt and fuel pump. Exciting!

Ex-rotor owner exploring the world of pistons and valves....