Hi ziggy
You can complete the entire answer on sheets of paper. Just make sure that you number all the additional pages and put your name and National Insurance number on them. Also make sure that it is clear which question you are answering. (I know that may be obvious but plenty of people forget). Then, on the form, I would put "see page (whatever number)" so they know everything is there.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems