Found a pair of England car flags for only 59 pence at HomeBargains. There are loads of them on their Star Buy shelves.
Have seen these sell for
£1.50 for a pair at Tesos
£1.50 each at Sainsburys and Halfords
This flag has the St Georges cross with the word ENGLAND written across.
This is the cheapest that I could find. First post so please be gentle!