thanks for all the replies, so the concensus of opinion seems to be that regardless of whether we were using a varistream etc or not it should have been replaced f.o.c. which is what we thought.
i am a bit surprised that the company we bought it from did not offer to do this, as they are very very well known to most of us on here, although they were very helpful and did, in the end, supply a pressure switch at a reduced price.
i think they were aware that they might have the same difficulty that alex has mentioned with regard to the manufacturer replacing it for them, it would have been nice if they had taken the same attitude as peter fogwill and stood by the manufacturers warranty regardless of the implications for them.
and no we were not informed that we had to have a controller before we purchased the pump, when i raised this point i was told that the spec sheet suplied with the pump also mentioned the correct circumstances in which the pump should be operated, i have to admit i didnt read that as i dint think it necessary, the only thing i did was to post on here asking which way up the pump should be fitted, i could not find a reference to this on the spec sheet
thanks again for all replies
the lesson we ahve learned from this is be careful where you buy from and to buy from people you have used before and had good service from unfortunately as has been mentioned the company we used in the past has stopped suplying pumps.