He has a secondary alternate, XXX, but XXX is further away than LPL- possibly much further away.
While he had plenty of fuel to hold if LPL was the diversion, his minimum divert figure to XXX is much higher
How much further away? We are talking about the UK here not Africa?
I can think of multiple suitable alternates around MAN not including LPL. You have LBA, EMA, BHX and BLK just to name a few. That is not counting Doncastor,Teeside or Coventry on top of that.
If he had "plenty" of fuel as you put it to hold he most probably would have had enough to divert to most alternates.
It sounds like the crew just let ATC know there intentions if the hold went on a little bit longer. Good practice and airmanship.
This would have alleviated work load to ATC in fact as they would have had an idea of the shuttles intentions if the situation would have continued. ATC would have been prepared and expecting the diversion and everything would have been set up for this possibly by the ATC assistants(if there is any working at the time). Just dumping it onto ATC's plate if they needed to divert and start heading towards the alternate would have been much more stupid.
Good forward planning. I think it was very good form to let ATC know in fact. Not trying to increase workload but you only have so much fuel and if you have to divert then you have to do it that is it.