Customer input on magento products

What we need so for some configurable products will have user input which will allow users to give a width and a length, plus select from a list of paper types to define the m2 price. From these inputs and the amount is worked out by m2 x width x length x Qty

I'm looking for UK based developer who has worked with magento before.

Budget given is just a rough guide. Please give honest values

If you require more information before bidding please let me know.