Anyone know of any places that are willing to give the underside of my car a good clean and maybe wax oiling?

It seems the previous owner loved a bit of mud/clay plugging.

 

have you got any haulage companies near you?

when my mate did his evo 6 he took it to a local haulage firm and drove it onto their truck wash ramp-gave the geezer £20 and he did it for him................as it was an evo tho it was rotten under all the mud etc and he had to then spend £1k on chassis repairs

if you are planning on undersealing it you will need to dry the car 1st-leave it in a garage until dry and maybe with a de-humidifier on aswell