I doubt the cold has killed tbh, ours lived outside for years in hutches and other than extra hay and food in winter and warm vegetable water we made no alterations for the cold.
They really should be kept indoors in winter in the UK... The cold and damp outdoors CAN and DOES kill.
RSCPA advice about Guinea Pigs:
Living in a draughty, damp, poorly ventilated or dirty environment can cause guinea pigs to suffer and become ill.
Guinea pigs are sensitive to temperature changes. They must be kept out of extreme heat or cold. Temperatures above 26°C can cause heat stroke and below 15°C can cause them to become chilled.
Someone also said upthread to get two or three females as a replacement as they are social creatures. I'd just like to say, that this type of advice is also quite bad, as it means that there are a lot of males that end up unwanted. If you look at guinea pig rescues they are overwhelmed by males (particularly single boars).
Males can live in pairs if they have a lot of space. Its true that sometimes they do end up fighting and have to be separated, but you can still keep them together as neighbours - that way they have their own territory but still have the social interaction they need. This shouldn't actually take up any more space, since two males kept separately, need the same space as two together anyway - if you house them in a cage that you could divide should the need arise, you won't have a problem if they don't get on.
In my experience males also tend to be more confident, outgoing and receptive to human interaction than females. I know that a lot of the regulars on the Small Furry Animals section will agree with me on that.