I am afraid I have some bad news for you.
I was recently at a party and was chatting with a couple there who both work for different major financial institutions. I have just signed contracts and asked, if there were anything that could go wrong now that I have the official letter of offer from the bank. The woman who works at the bank said that the only time she ever stopped a transaction and didn't issue the cheque after issuing the official letter of offer is when she heard that the company the individual was working was relocating. She said it was hard, but she had no choice as the person potentially didn't have the security to pay the mortgage. From what she said, she didn't know that the individual was definitely going to lose her job - just that it was in jeopardy and they still refused to proceed with cheque issue.
I know this is anectdotal at best but is something that does happen.
Best to speak to your bank and clarify your position. It might be an idea to quit or leave your job now and find another position before proceeding further with any conveyancing. You certainly don't want to be jobless and worried about paying a large mortgage.