Dear Moonhowl, XiaoLong & sooby,
Thank you so much for your replies, which I have just managed to open. The very first picture on the link from Moonhowl, shows exactly the beasts I am looking for- mealy bugs. I am familiar with mealy bugs on apple trees, but did not realize that there were other types. I am going to try first the water jet as I have exactly the tool for it. Thanks to all of you for taking the trouble to answer me. It seems here in the UK, we have similar bugs keeping us gardeners on our toes.