I'm not aware that demobilization was happening before the end of the war, but I guess its not surprising.

In terms of the economy - war isn't cheap. You need ships, aeroplanes, tanks, ammunition, artillery guns, uniforms, radios and many other pieces of equipment. You need to pay all the people enlisted in to the services and make sure they have food and shelter.

Everything had to be turned over to helping the war effort - production of cars, clothing, furniture - just about everything you can think of either stopped or fell dramatically.

Elder generations even now still say "make do and mend", they had to back then, there were no new things to go and buy.

Petrol and Food was rationed, the state desperately needed supplies and paid America to provide them (not least through the lend lease act). At the start of the war women were asked to give up old pots and pans that could be melted down and used to build planes/tanks/ships etc. People cut down their garden railings and donated them - all part of "doing your bit".

The point is the entire country was pushed in to war production and directly or indirectly the government was paying and it cost an awful lot of money, government income from taxation would barely make a dent in the expenditure.

If people were being demobbed late in the war I would suggest it was a cost cutting move, given that the end of the war was in sight. I forget the precise details but in the army there were a huge number of people involved in administration/logistics, if there was less fighting going on there would be less need for these roles.

You may be interested in reading "Wartime Britain: 1939-1945" by Juliet Gardiner that explains what life was like in the country during this time.

I'm aware that there are books on the immediate post WW2 era but I don't have a specific recommendation, maybe others readers can help.