What I ended up doing/notes for others:
The T30 reverse torx bolts
Having seen a story (I can't remember who) about stripping it, I opted to get new ones as recommended by that member.
I could get my torque wrench in for that one and set it to just under 8nm... however when I went to do it up, it got suspiciously tight and still did not click (my wrench can do both directions). 8nm really is very little so I figure maybe there is some give somewhere that wasnt letting me hit the torque (I saw the sprocket was rotating a minor amount) so I left it at hand tight.
The cylinder caps which this topic was originally about
I bought a set of long allen keys and this made winding it on SOO much easier than what I did with my socket. I had got the socket because I planned on use my torque wrench without realising it wouldnt fit.
The allen was quite long at 17cm+ so I could get pretty good leverage on it. I pulled quite hard on it but still felt uneasy. How much did I need??? Then I realised there's probably a calculation I can do to work out how much force/weight I need.
Torque = Length x Force
This ended up working out to be about 3.7 kgs of force on the end which isn't actually that much. I had thought 50nm was a tonne but its not. So, I went and picked up some weights and felt how much ~4kg was and... winged it.
First start
I was expecting the car to have some temporary grumpy idling as noted by guides but mine came back to life beautifully and idled nicely! Did a spin around the block and the car ran smoothly. I got it up to temp and then took it home as the coolant light had come on (expected). Will let the car cool down now and top everything back up.
Not yet put the C110 back in to see if the VANOS numbers are changed but I'll drive around for a while before doing that to butt-diagnose it first