I have donated my body to a medical school for student surgeons to practice on. Costs nothing and the school do all the arrangements for you.
If they do not want it then it is into a body bag (£11 on eBay) then a van delivery of the body to the back door of a crematorium for disposal.
Total cost is around £380 , death certificate and cremation permit £58 , van to crematorium £20 and the cremation fee £300.
I will arrange for a friend or relative who is on benefits to apply for a funeral grant which is £1200 so that leaves over £800 for an all day p*ss up at my local boozer for a memorial.
By the way it is 100% legal to just have a body in a bag delivered to the back door of a crematorium so it can just be put straight into the furnace for disposal with no ceremony at all. All you need is the death certificate, and clearance for cremation , plus a way to get the stiff to the crem.