(07 Apr 2023, 7:06 am)L469 YVK wrote Could 7401-06 be replaced with extra E400MMCs tagged onto the next Northumbria order?

If anything, any order for new deckers soon is required for the Durham County operation - let's not forget Darlington now have decker-operated boards on 1/5/5A/X1, 7s, X26 and X66 but still only have 7 E400s. Add to the need to replace the B7s and you're looking at a need for new stock.

(07 Apr 2023, 7:40 am)tvd wrote Whitby / Redcar should've had some of the new minibuses Darlington got, to replace the Solos.
After all, Whitby's Solos are just as old, and when spare are often required on longer routes as well as the 95 and 96, so surely newer replacements would be at least as needed there as Darlington.

There's a difference - Darlington's town work is commercially operated, whereas the 96 is tendered and the 95 has been cut back from half hourly to hourly which suggests it's not doing that great to support any investment.
It should be noted that originally, Stockton were due to gain some of those E200s for the extension of the 7 as they originally foresaw issues with parked cars around Kirklevington Village - in the end, the issue was more to be found in Yarm Station's car park but that has now been sorted.