i have exactly the same problem. i have paid Baxi £300 to come out and fix it, but the engineer won't touch it because he would need a ladder to lift the boiler off the wall and would not get another person or accept help. If it is more than 3 feet off the floor, he is going to need a ladder. I have never had such a waste of time and feel totally conned by them. DO NOT USE THIS COMPANY FOR SERVICING! the plumber had no intention of doing the job and their Ops Sp person is very rude. i now have a useless boiler and am worse off.
For what it is worth, the problem does seem to be a broken expansion tank and the boiler needs to be dismantled to change it.
For what it is worth, the problem does seem to be a broken expansion tank and the boiler needs to be dismantled to change it.