Bank transfers are pretty much instant, I always do this, carrying huge wads of cash around are not my idea of fun.
Bought my VX220, went to guys house, we sat in his living room after going over the car and paperwork and then hooked up to his wifi logged into my account, transferred the money, he logged into his bank and it was already there less than 30 seconds later. Did the same with the Skyline and the Celica. Each time the money went through instantly.
When someone bought the Skyline we walked down to the highstreet, went to his bank, put his card in at the cashier, we both checked the amount, put my card in, receipt for each of us 2 mins later we are both our paperwork swapped and money sorted.