lost his job two days before Xmas, - and yes he was a 'Head of'. He had a breakdown last June, and had been hoping (after trialling various medications that all had some fairly nasty effects on him) to return after Easter, for the summer term, but the school couldn't afford to keep paying him as well as a supply teacher, and also didn't want to risk it happening to him again. He was signed off every month by the Dr, and he had a term at full pay and after that, went down to half pay, when PPI kicked in and paid our mortgage. Sick pay from work runs out at 28 weeks, so his pay stopped a few days ago, with his last salary. He has received a lump payment from the school because they don't want him suing them for overwork, but frankly he is in no state to be able to sue anyone.
Yes, he will do supply teaching, and also exam marking and whatever else he can cope with doing. And as for supply teachers not being adequate - I'm afraid that is often down to the school, trying to save money by saving on little extras - such as my friend, returning from maternity leave, discovering that the school had not wanted to pay for ANY of her 'A' level students to have their homework marked! Apparently they can pay for bog-standard teaching, or pay more for all the extras.
It has really hit him hard, though. Despite being hugely overworked, he did love his job. The school only realised how much he did when they not only had to fund a supply teacher, but had to dish out all his other work between five different people. None of whom are all that pleased about it. I reckon losing his job has set him back about three months.
He left it too long, he thought he could cope, so I really think leaving may be the best thing for you. However - get yourself signed off for longer, and then see how you feel. Maybe aim to return after Easter. I suppose it's possible you just need a break.