I think they came close to acquiring some 767's which is a common type rating with the 757, i heard they'd got as far as buying some 767 ULD containers that were going cheap, probably sold them for a profit!!
But i think given current trading they are right to stick to what they know best and make the Midlands and North their own turf, i know some think their jet2holidays packages are a bit tacky and some are but its got to be great for cash flow when you've got £1000's sat in their bank account for 6 months
the 300 is still ideal for under 3 hour med runs and they get cheaper all the time