Thanks for the replies,
all the advice is welcome as I am still very much a novice.
Thinking back I only set to 128 while at the nav map and watched the contact spikes move along my plotted course for the convoy,when I had a look through the periscope to check on progress I was at 1x and when I was at the nav map my periscope was down so I was able to go to 128X.
I did notice the forward escort weaving or zigzagging but I thought this was normal and was just checking for contacts astern of it (in its baffles)also I have to admit that I was in what I thought was a good position to attack the convoy and did not even think about the fact that I was at 90 degrees to its course.I still have a lot to learn
I did evade them and get away and surface and carry out repairs with exception of the rear dive planes, and returned to the convoy to try and attack again but I do need to learn how to deal with the escorts because before I even got into a attacking position I was being detected and I didn't get away this time.
I am using the stock version and I havn't changed any settings (don't know how)
Bert