best mattress for edwardian wooden frame with spring base.

Hi
I have a double Edwardian bed base 55.5" wide x 77.5" long. The headboard is approx 56" high and the footboard 48" high. it stands 182 off the floor with a sprung base.
I am looking for an open sprung mattress that is fairly deep ( maybe 12") to reduce the height of the head and foot boards.
What sort of mattress would yo recommend for this type of base? This bed will be used in a self catering apartment. Needs to be durable abut not too expensive. Around £300 is really my budget.
Many thanks. Look forward to your response.