Getting Help to Repair a Patio Door Inexpensively in the UK?

I'm 76 years old and relying on the state pension, ie. low income and no savings. The 2 section patio door at the back of my 2 bedroom bungalow needs replacement because the sliding section has failed. At present it is standing on my lounge floor leaning against the fixed section. This has left a wide gap which is both drafty and a security risk. This gap is necessary to get access to my garden and to ensure escape in the event of fire.

So far I have applied to Independent Home Solutions, located in Reigate, who obtained a quote for a replacement patio door, but the result was £1600 and I was told the Reigate and Banstead council, who they act for, could not help because of the high cost. For some 2 months now I've been forced to keep my central heating on fully for much longer periods plus a electric fire to boot because of the present cold weather. I need urgent help but have " hit a brick wall". Could you please advise me what help I can get to achieve either a replacement door or one sliding section or even to just fill the gap with another construction including a door?

By Key S W