Need Cheap Mattress(I go it!)

I am at moment, looking for a cheap single mattress.

I can only see for £120-£140 or even more expensive at the moment.

Which is a price of a new bed!, I only need a mattress.

I have tried everywhere, ebay, argos, dreams, beds.co.uk,lazy beds, ikea

sales all-around all the same price.

UPDATED INFORMATION:

So I have been searching and I WANT TO THANK EVERYONE WHO GAVE ME IDEA'S, HELP ADVICE AND WEBSITES TO HELP ME.

Very greatful

Tried all the websites people have sented me and kept going back checking them all again.

Guess what I ended up at ebay where I 1st started!

There is a Memory Spring Memory Foam - Single

£47.68 Free postage

New condition...

Which I ordered hope its good.

Its only on ebay for next 6days

If anyone wants to know..

There are also value stuff on gumtree which had brand new single divan beds with mattress still in its packing betwee £50-£70

The time I kept checking Gumtrree.co.uk

weather at a warehouse or someone's address... The address's were 3hours away from me it was not worth it... but might be worth it for someone of you guys...