Thanks to some precise measurement by Milligoon I have just discovered that Aldermog has cut outs for the speakers already in place behind the carpet lining the footwells.

If you don't have speakers and wonder if fitting them is an option measure up from the floor 9" and forward from the door frame 4.5" and you should be about in the centre of the hole. Dimensions warrented only for a S2 Roadster, but probably apply to all wide body long door cars.
So I have no need to cut out the holes. I wonder if there will be speaker wires in place too?
To be honest the fitting isn't in the best place, but there are few options. I'm also concerned about the depth behind the panel as I suspect it is very restricted, so limiting the possibility for fitting really good quality speakers because they have big magnets.
The next job is to sort out a head unit and tweeters for the dash ends. The buy a load of Dynamat to line the footwells, doors and scuttle/body sides to keep the noise down.
This wil be a winter job, I'm sure. Along with the rear toolbox as per Dave Ws description!