Cost me £12 delivered.

bought on eBay aswell.

Really happy with it.

I read quite a view reviews before finally trying it.

It sealed/fixed it straight away. No increase in running temp.

& I'm finally returning ~340 miles a Tank. ( Was 260 when I had the HG leak)

Check that the radiator fins are all intact and haven't been damaged by power washer or clumsy handling.

Re: Update

Is there a tiny leak in the radiator.
I had one that peed out a really small jet that you could hardly see and then only when it was running hard. It took ages to locate it but the syptoms were very similar.

No my Rad was absolutely fine (& brand new)