Answered my own question about the HRC header, yes I can and it works well.
Stupid boy Oliver.....
Anyway, I still had (and still do have) a few niggles and a charging system to sort.
First thing I did was space the sidestand over to stop it hitting my exhaust. Got some 10mm spacers from thunderace and drilled those out to allow the sidestand bolts through. Anyone like my makeshift vice? (Dad stood on the molegrips

)

Unfortunately the sidestand still hit the exhaust. I had to leave it like this for a week or so as I needed my bike back to do a few shifts over in Lincoln.
Next was sorting out the coolant header. Put 100ml of coolant into the header and submerged the end of the hose in it, then filled the cooling system to the brim with no bubbles this time

. Then stuck the rad cap back on and ran the bike up to temp to get rid of the rest of the coolant in the pipe
Had to wait a day or two for some electrical goodies to come in the post then it was onto re-wiring the alternator to reg/rec.
First I sanded back the reg/rec mount on the subframe and re-mounted the reg/rec with new stainless nuts and bolts and some heat-transfer paste.
On advice from Neosophist I ran a new negative to the battery and also took out the house wire extension on the positive wire. All taped up to avoid confusion
The 3 yellows were next. I put a new 3 pin connector block on the alternator wires and made a new stretch of wiring from the 3 pin connector to the reg/rec plug. A good soldering iron and patience helped a hell of a lot here. Bare wires were sleeved with heat-proof fibreglass tubing and taped to keep them together.
Got readings from 13.2 from when I first started the bike to 14.7 (across the battery) after the bike had warmed enough for me to think it okay to put the seat unit back on. So that should be my charging system woes sorted for a while, touch wood.
I also added a nice little accessory. I hate not knowing the time.
Today with the snow and shitty temperatures I got round to sorting the sidestand properly. I took off the spacers as I wanted to use the fairing bracket properly. Drilled and tapped the stand bracket and put in a small bolt secured in place with a nylon locknut, then filed down the stand a bit to help with ground clearance. It needs a bit more filing but it's bloody freezing and I'm not going back in the garage now.
The last thing I have to fix is the air-leak in the carb rubbers. Seeing as the rubbers are stupid expensive I'm going to have to wait til payday for them to be bought. But with this current Arctic weather I don't think the bike will be leaving the garage for a bit anyway.....