swapping all my gear over to a new frame. it has a 110mm head tube length, my old frame had a 120mm.

is it just a case of some more spacers?

Yes.

or a bit of careful trimming with a hacksaw.

Yes.

don’t want to touch the fork (just in case I sell down the line.

Headset – any grease or special treatment? or just simply pop in?

I’d put a bit of anti-seize or just teflon grease on the headset.

Which frame did you decide on? There is a new Inbred with swap-outs coming out if that’s what you are going for.

got a turner flux 😀

just had a quick look on youtube – there where loads of special tools and measuring etc 😯