Pseudo-architectural exterior door-surrounds?

I'm wondering if I can obtain some sort of tasteful architectural front-door surround from somewhere that can be fixed to the wall after the doorway has been cut. Sort of like a fireplace surround, but made for a front door out of some durable material that looks like stone - and preferably not too expensive. The house ws built in 1900 but I guess any historic-looking door surround might work... Georgian, Neo-classical or whatever...

Anyone know of an inexpensive supply of such things? B&Q perhaps?

Thanks..

Brad J