You can live without many things, but you shouldn't cheap out on the mattress for your bed. Concerning the dimensions of the mattress, it measures 140x200.
From Amazon
Visco Therapy FOAMEX Recon Foam Mattress, Firm Comfort, Cleanable Cover, Silent, No Springs, Available 4", 6" and 7" (14CM Thick, EU Double)
OnBuy
(EU Double, 14 cm) All Foam Foamex Mattress, FIRM comfort