I was having a conversation with a couple of guys on the Poole run this weekend, at once point we got talking about blown radiators and how difficult it was to find replacements for some stuff. I mentioned that I knew and had used a great repair shop in Kent, but couldn't remember the name...
I've just found it... The Company is called GMX, the site say that they do Moto-Cross radiators, which would have fitted as it was a Yamaha WR450 set I dropped in, but I'm sure that when I was there they said the did a lot of other stuff to, including redesigns for better performance.
It was a few years ago that I used them, but at the time the gave excellent customer service. I'd pranged one of my rads a week or a fortnight before a trip to the Pyrenees, I rode them down (on a different bike) these guys repaired and re-enforced the pair and got them back to me with plenty of time to refit and get the bike back on the road for the trip.
http://www.gmxradiators.co.uk/
Gooz, it might even be worth talking to them about the rads on your Suzi, one of the things they were able to do was redesign existing stuff to get more cooling for the same footprint... as I say, it might be worth an ask.