Originally Posted by
William Treseder
A new expansion vessel for your boiler will cost in the region of £100, plus cost of heating engineer/plumbers labour. If the flue on your boiler is vertical, it should only take an hr at the most to replace it. If the flue is horizontal and crosses over the expansion vessel then that will take longer, as the flue will have to be removed and replaced (and tested again)
You could pump up the pressure in the existing vessel with a bycycle pump to buy some time, but ultimately you will have to replace the vessel or the boiler if you choose to.
Beware if you try to get cover on a boiler that already has a problem like yours, as some companies will give you cover, fix existing problem but will want you tied into a long term contract.