Don't want to bog you down with the boring stuff, but how will you go about MOT etc now?
If you'd read the full story you'd know. He's kept the original taxi chassis as near standard as he can so it still meets the requirements under the points system to not require an IVA test, it will retain the identity of the original taxi. It'll just have a change of body type, engine and fuel. So it will go for a normal MoT but emissions will be based on the age of the engines or chassis, whichever is the earlier. Everything else is pretty much common sense, lights, brakes, etc will need to work but it will still be tested to the age of the chassis so anything that has been introduced since then won't be needed.