what a load of s***te, have ya read pp's post on servicing isars in the cc
I would love to see an isar/icos serviced with a vacuum cleaner
If you cant figure out where to remove screws to get into the boiler you have no hope of solving your poblem. If you m-series hasnt been serviced for a few years theres a good chance you could have issues with insulation boards.
Ring ideal/warmsure. It will need a thorough strip down.