Attached below is a photographic record of the first day's work on this conversion. The Mk1 coaches were picked up cheaply from a local model shop. I used 2 BSKs for this conversion. I made a bit of a mistake, however. What I'd thought on first glance were 2 Hornby coaches turned out to be 1 Hornby and 1 Mainline. This caused some issues with the thickness of the coach sides when rejoining them, but nothing that couldn't be rectified by a little filing. I used the Hornby model as the 'base' for the chassis, roof and sides; and used the mainline sides to fill in the missing windows etc that I needed.

It's worth saying that I've been working purely from photographs rather than scale plans, and that the window positions are estimated rather than precise. I'm of the opinion that if it looks right, it is right.

The first step was to plan the arrangement of the new coach sides. I numbered the plans and numbered the corresponding pieces of plastic on the back to avoid confusion:

Cut:

Fit:

Shut. I used styrene rod to reinforce the joins. It's important to leave enough room to glaze the windows:

Testing the fit of the new sides in the coach chassis:

And the other side:

The joints in the coach side were then filled:

And sanded. I then sprayed a coat of primer to identify areas that needed further filler or sanding:

The coach ends with detail removed. New windows still need to be cut:

Test fit of the remaining 'normal' roof section:

And again: