Hi all,
I had another plumber come around for a second opinion, and wanted to keep you guys posted - in case you were interested.
In a nutshell he said the leak is fixable and some 'spark' bits need changing, and will give it a service. He did say any further issues going forward and it will probably be best to get a new boiler. So, I've opted for the temporary fix and will wait till the boiler eventually packs in before getting a new one.
He did say it was safe to use in the meantime as there was no gas leak and/or major leakage. This means I can shower - thank god!
NewBee