Go to a place where they sell front doors (B&Q or a specialist supplier). If they don't fit doors themselves, they will probably be able to sub-contract it and/or give you the name of someone. This is what we did, except that I stained and varnished the door myself.
You can get new front door from most places... try you local hardware store they should know some one or your local joiners. BnQ is very expensive and should only be used in emergencies. i had a barn door with cat flap, stained, locks fitted, new frames for around door and fitted for �320... dont pay any more than that