Mortgage Offers on a new build property

Hello All, I was hoping that one of you may be able to help me.

I have recently reserved a plot on a new build development which isn't due to be completed until April/May 2014!

As I have reserved the plot the builders require me to exchange contracts within the next 28 days.

The problem I have is that there is no mortgage company that will give me a mortgage offer that far in advance. I did speak to a broker who said that there was one company that would give a mortgage offer for 10 months but they wouldn't give me the name but did say that they were a fairly major lender. Does anyone know who this is?

I've also heard about mortgage companies "extending" the mortgage offer if the build gets delayed but I assume the original completion date for the property has to be within there normal mortgage offer (usually 6 months) term.

I am VERY reluctant to exchange on any property that I do not have a mortgage offer for. This could be financial suicide.

The builders are pushing hard for me to get an offer but rightly so no bank will give me a mortgage offer for a property that completes so far in advance. From my point of view, there is no point getting a mortgage offer if it expires before completion. That's the same as exchanging without a mortgage offer and serves no purpose. Does anyone know different?

Has anyone got any advice on what I could do?
Does anyone know the name of the company that does a 10 month mortgage offer?
Am I able to do a conditional exchange subject to me getting a mortgage offer? Is this usual and is it likely to to happen?

Any help or advice is greatly appreciated.