If I was you, I would hang on in your current job - until you have got the keys to your new house in your hand. Until then there is a chance of something going wrong eg the seller pulling out, the survey throwing up a major structural or planning problem, a counter offer being accepted, your application being selected for an internal bank audit etc. etc.
Any of these could mean the deal is delayed or falls thru - so that additional information is required from your employer.
I know the commute is painful but doing it for slightly longer will surely be worth it if you get the new house and lifestyle you want. I recently left my job and could not wait to get out, I had to work longer than I wanted but in the end it didn't make any difference. Stick it out - it will be worth it.