"JWH" wrote:
Many thanks to all, (except John). Since the washers were only a tad
oversized i assumed that wasn't going to be a problem and it was something
complicated like an air lock. I got a scapel blade and shaved carefully
all around the
washer to get it to the original size and bingo, it all works fine. we
novices do suffer you know. thanks for your kind patience.

Well done, you can't get more DIY than that!