The reason they insist on 35 minutes from Security is that many flights departs from T5B and require a one way transit link. It is far from straightforward to get a departing passenger back from the T5B without an escort. You cannot simply reboard the transit as you are then mingling with arriving passengers.
Munnyspinner I have little sympathy as the deadline was clearly marked in any booking confrimation I have ever receieved from them. Perhaps if you paid more effort to reading than ranting you would get on better. As for BMI, they go from bad to worse in my view.