200+ new deckers is not that large an order considering the size of the group fleet, even more that they were pretty much concentrated in generally only two areas i.e. Manchester & Leeds.
What is likely to replace the remaining step entry deckers, single deckers? Surely First Group aren't planning to continue to use these up until the end of 2016 when DDA will deem them surplus to requirements
Difficult to provide a full picture but based on those operations that I've seen recently/experienced....
First Bristol and Avon - the step entrance decker is actually no more. The really elderly kit is made up of SDs with step floor Darts, early Lance SLFs, early Dart SLFs so guess the Streetlites due (and some service changes) will sort that.
First Somerset - a number of Olympians still working on Taunton routes to Axminster, Yeovil and Tiverton though some are confined to schools. Service changes will reduce PVR and see the last step floors at Bridgwater go.
First Dorset/Yeovil - the oldest Olympians are now S reg ex Bristol and are seeing some regular service (esp in the summer) but there's a number of step floor Darts at Yeovil and a number of R/S reg Darts at Weymouth that are due to go.
First Wyvern - hardly any deckers (what it has are 51 plate or newer) but a few ageing R reg Darts
First Manchester - some ex London Olympians in Rochdale/Oldham (are the Arrows on schools?) but mainly Geminis or e400s but some P/R reg Dart SLFs and B6s still working hard round Bury and Oldham
Would think the priority is to get the oldest single decks replaced as they tend to be in all day service. The deckers are more schools though in some places, they will need to be sorted.