Hi Alex, Congrats on the car! Sounds like a nice one too!
The radiator is a 'known issue' and I would say we all end up replacing them at some point. I had mine done representatively when fixing something else that involved removing the front clam.
I went with this one from Elise parts https://www.eliseparts.com/shop/engine-br-gearbox/cooling/aluminium-upgraded-radiator/ check it fits your car first (the site shows model compatibility).
But there is a cheaper aluminium one on there which will probably do the job perfectly also. The upgraded one runs my car 1-2 degrees cooler but more importantly the temp is more consistent now also. It gives me peach of mind. Don't be tempted by the triple pass one because they're not designed for sitting in traffic (unless its a heavy duty track car i guess).
Cost: you're looking at the part, shipping, and then 2-3hours labour clam removal, not sure how much for the job specifically sorry, because i had other things done. But at that point its probably a standard rad replacement.
The only other thing to be aware of is does your car have the optional twin oil coolers? they need to be removed when removing the clam and they are often seized oil meaning the fixings break and you need to replace them at the same time.