The prices are listed below. This is just speculation
Class 91 - £89.99
Mk.4 DVT - £28.49
2 Mk.4's - £56.98...
Then that brings it's grand total to about £175.xx.
It could be the older tooling. But I highly doubt a price rise of about £34 could be in existence for a train pack that includes a cheapo loco and DVT and similar standard coaches. I mean looking at Hornby prices for these, they've clearly reached a limit. How many will buy a Class 91 that's going to go over £100.00? And how many will actually buy a DVT and a coach of such inferior quality if it goes above £32.00?
What can actually justify new tooling is this:-
Currently the Mk3 DVT retails for £56.75 (the Mk.4 DVT will be similar if re-tooled).
That leaves about £153.xx left. That's the exactly price most super detail locos are hovering about at the moment.
You can use the forthcoming Hornby Class 71 as a comparison. It is priced at £149.99. Very similar to the Class 91 - both are Bo-Bo, both have a single pantograph, both have 2 cabs, interior electricals on the model will be similar. etc.
Just saying. Nothing concrete, but something simple to vouch for a re-tool.