Hi Julie
You are right to be cautious about what you send in. If you tippex out information, the chances are they will be able to tell information is missing, even on a photocopied copy, and they might wonder why. Ask yourself whether you need to include the letter if it doesn't support your case. If the information is irrelevant, I would just put a line through it - or black it out and say why you have done it. But, at the end of the day, only you can decide what you should send in.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems