When Lincoln station was closed for re-signalling a few years ago (two summers in a row) all services were provided with replacement buses. Due to the scale of the operation, there were huge numbers of buses and one Crewe based bus company even set up a temporary base in Lincoln employing local drivers to drive a few ex-Cardiff Leyland Lynx. It actually went remarkably well both years - the second (2008) was slightly better on the whole, with more control staff out and about at rural stations etc.
My most recent experience was on a Sunday, when the first Northern service out of Lincoln was cancelled (never found out why). The bus had come from Rotherham, and departed Lincoln some 15 minutes late with hardly any passengers onboard. There had been contradictory information given as to where the bus was to meet the train, some thought Retford and others Worksop - the driver seemed to think he was going through to Sheffield. The journey didn't improve as a woman started pestering the driver about using the toilet - she insisted on checking for one at Saxilby, the driver pulling into the car park and almost getting stuck in the process. She wanted to try the same at Gainsborough Lea Road but was stopped by other passengers. Rather than wait till Retford, she insisted the driver stop at a pub and disappeared for 10 minutes. The coach was now late, so the driver drove like an idiot into Retford, where a number of passengers decided to try for the train. I've no idea what happened on from there, apart from a complaint to Northern who apologised, reffered matters for investigation and sent a complimentary voucher.