Changing a CPU because its fan is failing is a bit like changing the car because its ashtrays are full.
Have a look at any of the UK firms that sell accessories or components.
If it is the sort of fan which is screwed on top of the finned heatsink it can be exchanged very easily for a new one. Prices roughly £5 - £50 with perfectly good fans costing either side of £10.
Do check the dimensions of the required fan and where to fix it. There is usually a dedicated lead which plugs into the motherboard