They look like this? Just seems impossible without ripping/cutting off the rubber hoods?!

they peel back a bit like a 1 more than 3 skin

eh ? you pull the lever and thread it in from the front – it will then come out the rear – slide on the outer and pull back the rubber from the bars a wee bit and the cable outer will seat into its slot

I use a 6mm drill, just behind the "peak" of the grip, then angle grind a little slot for the inner to pass through and Bob's yer uncle

How do you take the rubber hoods off to fit cables etc?!?

What else are you planning on putting in there?

as there shimano brake goes in from front if sti levers the gear goes in from side

If its just the brakes and no gears, then release the cable bolt on the calipers and as trail_rat states, pull the lever.

Single speed?

It is single speed.

Sorted- was worried about being too firmhanded but they are quite robust (ie. splitting risk).

Rear caliper wont fit through the rear caliper bolt hole in the frame though so academic really.

Well that sound wrong as well?

The bolt on the caliper is too wide. Hole (frame circa 30yrs old) too slender. Old brake caliper on front is a Shimano RX100

So it's the caliper bolt is too wide for the frame?? never heard of that before, does the front fit? it would seem rear weird that the front and rear weren't the same size bolt holes. If you want to return the rear you can have your pound back 😉

bend 'em over like a **** *** ***ing, **** ****em then yer good!

You almost certainly have recessed bolt calipers and are trying to fit them to a frame designed for standard calipers.

You can tell the difference pretty easily – recessed bolt calipers are fixed by an allen headed "nut". Pretty much all modern brakes are recessed fitting.

Standard ones have a threaded bit that protrudes through the brake boss, and are held on by a domed nut.

You convert from standard to recessed with the aid of a drill bit – drill out the brake bridge until you can get a recessed fitting in there. You can DIY it or get your LBS to do it – mine did my Raleigh for me, and it's been stopping with me on top of it for years now.

Sheldon Brown tells you all about it here:
http://sheldonbrown.com/gloss_ra-e.html#recessed

Ah! Will conduct two LBS interviews. Ta Tron. One will umm and err then say leave it with them and the other will say 'yep know it' 😀

+1 @tron. Did it myself a few months back. Very easy.