Spent another weekend working on my '71 S2 and more good progress was made. The front and rear suspension, steering and gear linkage is all good to go. Just needs a nut & bolt check, going over to check all torque settings are correct and I need a small piece welded for the rear gearbox mount. A few other small jobs and I'll be ready to put the body back down on the [new] chassis.. for the first time in 15 years 
Don't forget, there is a small (3/16" tall) spacer UNDER the heim/ball joint on the end of the shift adapter off the end of the transaxle. If you just snug up the nut on the joint...the joint will bind against the nut and loosen up in the arm. Not that it won't shift properly, but the joint will always be loose. See first photo.
I'll be ordering new silicon hoses from Banks shortly, but I also need a new radiator. Does anyone know which ones fit? I unfortunately no longer have a radiator at all, so have nothing to compare it to and I'm assuming something like a VW polo rad' will fit?
Patterned radiators (aluminum) are all over EvilBay like flies on you-know-what. That's your best choice: the mounts are in the right place, the baffle is where it needs to be, the hose connections are on the right side and in the right place, and, from the few I've seen, they just fit, rather than trying to make something work that was not meant to go in that space. Also, don't forget to reinistall the fiber closing pieces at the rear of the nose that cover the steering rack and so forth. If you don't...you won't pressurize the chamber enough to get airflow through the radiator and you will overheat. If they've gone walkabout...make some. I used 24 thou sheet aluminum. See photo 2.
Brake pipe to the rear, do you run the pipes through the chassis? I'm assuming you do, but someone might have a better idea?
As BDA said, from the factory they ran under the backbone. Some, as he said, mount them up on the side. However you do, use padded Adel ("P") clamps so 1) you don't get dissimilar metal corrosion and 2) a more secure mounting. See last photo below for example. If you do run new kunifer line, the original "T" clips are probably past their 'sell-by' date, so I'd go with the proper size adel clamp and use the holes the "T" clips were in to locate the adels and use stainless sheet metal screws to attach. (in fact, unless it's structural fittings, I replace all the oem steel screws, washers, and such with stainless. But that's a different story so I don't thread hijack...)
Windscreen surrounds: Mine is very ugly. The silver plastic is massive and just doesn't look very nice. Is there a better option?
I'm still a way off of having to worry about such things, but I think it every time I look at it!
You are limited by your imagination. Some re-set the window and fill in the gap with urethane and get chrome trim that sticks on/glues on to cover the joint. Others save the original trim (since it's been long (as in since the late 80s) unavailable) and do a chrome vinyl wrap, others? If you do attempt to remove the windshield...take your time. As I work around the periphery, I use wood shims to hold the glass (or plastic...depends on what you find at the hardware store) away from the cut mastic/butyl. Remember, the fragile part of the glass is the edge; nick the edge and you will get a runner. Time, patience, and minimizing the use of metal tools will go a long way.
In the end, it's your car...what makes you happy?
Oh and the final dumb question is the callipers/disks are from a Triumph Spitfire, right?
They are the same body...but the drillings for the bundy connection are different, so if you use Spit calipers, you'll have to bend up new hard pipes to go from the flex hose to the caliper.
But if you still have yours...they can be overhauled, repaired, and will work fine. The pistons aren't a close fit in the bores...there's a quad seal in the cylinder that centers the piston in the bore, and with some judicious cleaning up, new seals, a lick of paint (if you want...I did mine in red just because...) and you're good to go. I've never tossed what looked like trashed calipers...always was able to return them to use. Haven't tossed one yet. Stainless pucks, new seals, new bleeder, set of pads, pins, anti-rattle...takes an hour or so to do both of them once they're cleaned up and painted. I always preferred using the originals since the fluid inlet was where it was designed for in the car (in the center of the back) and the bleed was where it needed to be (at the top) to make it easier to get working. Just a thought.
