Nothing wrong with paying a premium for the market leading product delivered earlier, in my view. Israel for example have done the same seeking to vaccinate all over 16s by April I think.
The question really is where the UK goes from here does it maintain it’s lead or does mass vaccination get bogged down in delivery problems, logistical challenges or random other delays. If so, running “into the lead” looks more a political stunt than a coherent vaccination strategy. As ever, the proof will be in the pudding.