(26 Nov 2015, 5:13 pm)GX03 SVC wrote All the UK Bus operations have the same standard fleet number so there's probably most of 220xx-226xx across the UK. I think Stagecoach put these vehicles into random numbers before having the "by delivery date" policy of fleet numbers. Kuyoyo or someone like that will be able to explain further I think.

It's a result of when the national fleetnumbering came in to being (2003) - prior to that, all vehicles were numbered in local systems (one for Busways, one for Transit etc).

So vehicles delivered prior to 2003 were retrofitted into the national numbering system when it came into being.  As has already been said the two digit prefix is determined by vehicle type (22 in this case); where possible the last three digits were matched to the three digits in the old style registrations e.g. T495BNL became 22495, V675DDC became 22675.  There are exceptions where two batches shared the same digits, in which case the larger batch got the matching numbers, with the other batch fitted into the system elsewhere.

Vehicles delivered from 2003 onwards were allocated the lowest available series of fleetnumbers - hence the earliest deliveries in 2003 being numbered 22011 onwards, the 2005 vehicles being numbered in the 2234x series, 2006 arrivals being 224xx etc.