Hiya mate...
You can by a half reasonable mop for not a lot of dosh...the cheaper ones wouldnt put up with everyday bodyshop use but I have seen em for 30-40quid when on promotion....
Probably better to buy your own and then you have got it for good, wont be cheap to hire I wouldnt think...
http://cgi.ebay.co.uk/CAR-POLISHER-SANDER-SOFT-START-6-SPEED-FREE-KIT_W0QQitemZ330384675020QQcmdZViewItemQQptZUK_Body_Shop_Supplies_Paint?hash=item4cec7610ccI would recommend the farecle G-mop system for the pads and foams...always give good results...be very careful not to pick any grit up in the mop head or you will wreck the paint...washing the car first is a good idea to get rid of anything gritty off the paintwork...
Mopping compound, use farecle G3....keep it wet, squirty bottle with water in is useful...and watch out for edges and swages in the body as you will cut through to primer real quick...Try and wash off the splatters as you go...G3 dries like concrete on a sunny day...
Finish using a machine glaze to get rid of any swirl marks...the 3m glazes are good and give nice results...
THEN WAX IT STRAIGHT AWAY to give it some protection, after washing off the splatters..or it will fade in days...
Would say you can have mine....i rarely ever need to mop anything after painting it with the products available now..
but it is handy bringing laquer back after its been knocked back after burying metalflake!
Hope this helps mate...
Gregster