repairs needed to tyrolean finish

Hi,
I've got an 1890s mid terrace which is coated in tyrolean. I am about to paint the house. Most of the tyrolean seems reasonably solid, but there is an area at the back where it's blown, and the brickwork is damp and crumbling. I've pulled away an area of about 1/2 a square metre with my hands.
I am trying to get some quotes. One guy said that the whole lot needs redoing, and that I need to pull all the tyrolean off myself, and then he'll re-render it for £350.
A few questions:
a) Does the whole lot need doing now, or can I get away with it for a couple of years by doing a decent paint job on it?
b) Roughly how much should I expect to pay to get the back of the house re-done? Is that quote suspiciously cheap?

Many thanks for the help.
Neil

Well I am the woman of a builder...lol and hear talk about how jobs are done. At the moment my husband is making an estimate about a house that needs work on their tyrolean walls. I heard my husband say that you can check the state of the tyrolean by knocking on the tyrolean. Hollow sounds mean it needs to come of, solid sound tyrolean can stay on. Then apply a rendering coat onto the exposed places as an undercoat. Then you have the choice to render over the whole wall so that you have an evenly smooth wall to wich you apply your new tyrolean. If you don't wanne do that now but as you said later on than only put your new tyrolean over the newly applied undercoat rendering you put into the open spaces. This will not give the most perfect result as you will probably not able to smooth the difference between old and new tyrolean but it will do until you are ready to do the whole wall. Hope this helped.

Husband said yes suspisiously cheap if it is for the whole front of the house. If you take the tyrolean off yourself the person who is going to apply the tyrolean then firstly he needs to put a rendering coat onto your walls otherwise your brick work will show through your tyrolean wich is a poor show. And tyrolean is not cheap material so those 350 pound cant be covering the materials either. Better go with someone recommended to you if possible. There are many honest builders around but yes hard to find them through the cowboys....lol