I am failing to see how that isnt enough for 1 adult and a cat to be honest.
How many days do you know you will be travelling and is the £2 each way ?. Add this up and take it off the total
What do you normally eat? If it was me I would buy the following
3 x 500g packs of beef mince, potatoes, carrots, onions and celery 4 tins tomatoes couple tins kidney beans, 1kg pasta, rice, chilli powder etc Split the total into 3 and make a chilli, a cottage pie and a bolognese sauce each of these should do you three meals so freeze 2 portions of each so that's you got 9 nights worth of dinner with generous portions.
Pack of sausages and make a sausage casserole will do you 2 meals using some of the carrots, onion, Celery and potatoes from above.
Tray of chicken thigh and jar of curry sauce and do a curry, a chicken casserole and a traybake. Maybe get some peppers either frozen or fresh for the traybake and the curry to bulk it out. Serve with rice potato or pasta.
Get some cheese, milk, butter and flour and make macaroni cheese,
That's your evening meals pretty much accounted for.
Make a large pot of soup each week. Get some lentils or brothmix carrots, onion, potato whatever you have really. Take this to work for lunch.
Breakfasts can be eggs in various forms, but a couple of dozen and you can yes them for omlette etc for lunches or dinners as well. Buy porridge and weetabix, bread and milk.
That should leave you plenty for some fruit like apples, pears, tangerines bananas.
There will be enough left for plenty of cat food.
That wouldn't come to anywhere near your £245.