I have Crohn's and have had several chats with caa medical at Gatwick. They are thoroughly nice people who really seemed to want to help.
I think you will find that as you already have a class 1 medical there is no immediate panic.
The feds view when I called up was that as I already had a medical there was no problem.
Crohn's comes and goes throughout life, the average gap between attacks of Crohnes is about 7 years and there is basically no reason to have to stop flying while it is in remission. Whilst having an attack one may have to stop flying whilst on drugs or post-operative but these are normally short bursts.
So saying Crohnes is different for everyone and there is a wide range of possible outcomes. Best thing to do is chat to Gatwick directly, its the only way to get a concrete answer for your specific case.
Hope this helps.