It is 100% legal to just have the body delivered to the back door of the crem in a shroud or body bag, no coffin.Then just cremated without any ceremony at all. No need to use a hearse for transport an estate car or van will do (or even a hand cart) This will only cost the cremation fee (£350 near me) and the cost of transport plus the body bag (£11 on ebay) and the death certificate and cremation release fees ( about £75) so all in £450 including the transport cost, less if someone can give the stiff a free lift to the crem. Get someone on benefit to apply for a funeral grant £1200 and that leaves £750 for a ***up at the deceased 's local pub in memory.
Alternately leave your body to a medical school for the students to practice on, there is a shortage of bodies for medical students at the moment so plenty are needed. This is free of any charge , the medical school does all the arrangements and paper work.