Main PC XP SP3 has failed after eight years.
Thank god. At least that prevented you from using it post-April.
Which would you do ?
Tottenham Court Rd
GOD NO !!!! Even PC World is better than submitting yourself to Totty Road !
(for avoidance of doubt... I am not recommending PC World either, by any stretch of the imagination ... I would not be seen dead in either location)
To be honest, in this instance, its not "what would you do ?" but "what would you do if you were in my shoes ?".
To be honest, it looks like you have de-minimis computing experience, so I would suggest you accept the slight premium in price, slight reduction in choice and get your backside down to John Lewis/Peter Jones/whatever they call themselves these days At least then you are assured of a "reasonable" price, a "reasonable" selection of computers.... but most importantly, you are guaranteed no fuss post-sales customer service if you are not happy with your purchase.
Go to Totty Road or PC World and you're only going to get royally screwed by greasy sales reps who will be able to see your obvious lack of techy knowledge and so will take much enjoyment from flogging you stuff that gives them maximum margin.