Bed slats have dislodged and springs sticking out of mattress

i have a double bed, 3 yrs old and its has curved slats. the slats have become sdislodged and the springs in the mattress are poking through the gaps in the slats- i will never buy a budget bed again!!!
i am only 5 ft 2 so i need a lowish divan bed, some i have seen are ridiculously high. i like the idea of the pillowtop mattress and i am want a medium firm king size mattress as my partner will be moving in soon. he is 5ft 11. we both weigh 15st so i would like some help with a choice of mattress. i have been told pocket sprung is best. can you offer any help at all
thanks