Unfortunately as Ryaner said, your bank will look for a letter from your employer stating that you have a full time, permanent, secure job etc. Your upcoming redundancy would rule you out for most mortgages. In reality, you are probably better off not taking on a mortgage if you are likely to be made redundant, it'd put alot of pressure on you to find a new job.
It might be better to approach the banks for a business loan in order to buy the shop.
I'm not sure what you'd need to apply for such a loan. I guess you'd probably need to produce a valid business plan etc.
If I was in your boat I would use the time between now and year end to investigate this option. For example, you could speak to the bank to ask them about their criteria for business lending, you could enroll in a course on starting your own business etc. You could look for part time work in a shop to see if you'd like it and learn the ropes etc.
For me, looking for a business loan seems like your only option.
Good luck with it.