Home DIY

I would be VERY wary of this builders suggestions, they are likely to introduce far worse problems than they seek to solve.

There is a huge knowledge gap within the building trade when it comes to working on old houses - applying modern building techniques and materials to old houses can be a recipe for disaster.

A lot of good info here: http://www.periodproperty.co.uk/discussion_forum.htm

Agree.
I recommended lime wash or microporous
paint to allow the old wall to breathe.
The cellar wall is bellow the damp proof course there will be moisture build up in the walls, if you seal them the moisture cannot easily vent out which will cause problems the least of which would be the seal 'falling off'