The ending <cester> is very common in British place-names. It is usually pronounced stə. Here are some examples, but watch out for the part before the ending. That can have a surprising pronunciation too:
Bicester ˈbɪstə
Gloucester ˈɡlɒstə
Leicester ˈlestə
Towcester ˈtəʊstə
Worcester ˈwʊstə