Species will need to move out of the country to colder climates so the amounts and types of species decreases in the area. Some will even die out (extinction) if they can't move out; this could lead to mass extinction of a whole species.
Thats all i can think of right now, i will try to add more another time :)
The Thames Barrier was only built to protect London for 50 years. If the polar ice caps were to melt then rising sea levels could potentially flood the City of London which has been nicknamed the capital city of the world so if London would flood then it would affect many businesses worldwide.
Global warming would increase the temperature by a couple of degrees for the UK so more chance of heatwaves in the summer.
Also the rising temperatures would affect food prices. They may get cheaper because the UK may get hot enough to be able to grow it's own tropical fruits so they wouldn't need to be exported