@PhotoJim
T-Mobile and 3
entered an agreement to share their networks last year and later T-Mobile announced
to shut down 5000 of their own basestations.
Of course the 900MHz band requires less basestations and so is cheaper when it comes to roll out comprehensive coverage, but after a merger of T-Mobile and Orange these guys will have
60 MHz of continious spectrum in the 1800 MHz band and 20 MHz in the 2100 MHz band! Vodafone and O2 have only ~12 MHz of fragmented spectrum in the 900 MHz band and ~10 MHz in the 1800 MHz band each, while their 2100 MHz spectrum amounts to 14 (Vodafone) and 10 MHz (O2).
I'm convinced, there will be antitrust requirements for this merger, forcing T-Orange to return some of their spectrum. Otherwise they would have a huge advantage in network capacity, which will become of relevance when LTE comes, since bandwidth on LTE will depend on the amount of continious spectrum.
I don't know Ofcom's plans on the digital dividend, but like in other European countries I can imagine, that they will combine the auction of 850MHz-spectrum with a comprehensive refarming of all former GSM-bands, so there will be more or less equal conditions for all operators.