Hi Phil,
Welcome to the club!
Do you find the top of the rad that it is plastic and is crackled?
Not cheap to replace a rad and the top part of the rad is not repairable.. however.. I have had a leak in mine for over 2 years... I just keep checking it every week and only loose half a cup full a week.
I reckon a new rad be in the region of £200 + Vodka & Tonic (VAT)