Further to this,I managed to track down the original owner of this enclosure,and he told me that the original drivers were actually designated 'Trace Elliot' and that he actually had one that he had kept in his shed for what ever reason,and ,true enough it was.A lot flimsier than the Eminences that I've installed,I must say.He then told me that he had replaced those with much heftier units after about 5 years,and then,after that,the ME10s.So this unit has never had Celestions fitted.But with a couple gigs under it's belt since fitting the Alpha 10s,it's sounding fine.I've managed to procure an old HH 15" cab with an Eminence driver fitted,so I'm going to start using that in conjunction with the 4x10.
I still think that since starting to use the Squier P5,that this has been a major contributor to the problem.I use the low 'B' quite a lot,so having the 15" will actually cushion,or help to cushion the wear and tear on the 4x10.Time will tell,I guess.