Hi and welcome!
Please bring your piggy inside if at all possible. Guinea pigs are NOT winter hardy, and it is particularly cold at the moment. they need to be treated like you treat tender plants and need to be ideally kept in stable temperatures between 15-25 C all year round. They can also die from heat stroke during heatwaves.
Cold Weather Care For Guinea Pigs
Hot weather management and heat strokes
Please see a vet before the weekend for cheilitis. This is a lip infection caused by too much acid in the diet. In advanced stages it can be fatal.
Guinea Lynx :: Cheilitis
Please stop feeding any fruit and tomato altogether from now on as they provide the acid that has caused the problem; too much and/too often causes tiny cracks in the skin of the lips and mouth through which bugs can get in.
Please reduce the veg to 50g per piggy per day and the pellets to 1 tablespoon of pellets per piggy per day; over 80% of the food intake should be unlimited hay, hay, hay for long term health and a long life.
Long Term Balanced General And Special Needs Guinea Pig Diets
Here is our list of recommended UK vets:
Recommended Guinea Pig Vets