Its not very often companies get my seal of aproval so much so that i'd go to the effort of writing a review, but this company definately gets my vote.
Their website is: http://www.adrad.co.uk and for the vauxhall page:
My radiator broke for my z20let and i needed one asap.I rang vauxhall and the first garage i rang said "we dont know which one you need" well that was helpful..
The second one said, they could get me one, and it would take about 4 days before they even had it in stock, and it would cost £128 + VAT (£150 ish).. and the fact i'd have to go and collect it, as you would expect (having no car makes this difficult).
After speaking to a few companies, it was looking like it would be atleast over £100, and a few of them were Non GM products.
Finally just before I was going to order one, i stumbled across the company Adrad. I emailed them and they advised me the exact one I would need (GM456) within a few hours. After going onto their website to check the pictures of the radiators with all the measurements, i compared it against my radiator just to see if it was the same, and it looked it.
I ordered the radiator on the Thursday at about 2pm. By Friday lunch time, i had this at my work address, packaged securely and totally undamaged, and for the great price of £48.75 + VAT + P&P. I think the total was around £60.
Considering this was a GM product delivered in less than 12 hours, i thought that was a great service, and a great price, mega pleased with them!
So if you're looking for a radiator for your car, i 100% recommend Adrad!