Thanks very much chaps.
Andy, yes, the fit of the resin parts seems very good, apart from the plug for the mid-upper turret, which is rather vague in the way it locates, and, being rather thick, it's quite heavy, of which more later.
Herman, if I need to engrave a long, straight line, then I use a piece of 'Dymo' tape, stuck in place as an edge guide. The resin template was indeed a nice touch, and worked very well.
I've got the new windows cut, the 'redundant' windows blanked-off and filled, and the resin 'plug' for the mid-upper turret position attached.
PICS 1 to 3. A length of masking tape was first laid across the existing windows, and the shapes cut out to provide a rough template for alignment, spacing and size. The tape was then placed into the required position, using the cut edge at the rear to achieve the correct spacing, and the shapes were then scribed, using a sharpened compass point in a pin vice.
PICS 4 and 5. The roughly scribed 'windows' were then drilled, and the windows cut and filed to shape. Rather than use the kit windows, all of the windows will be glazed with Humbrol Clear fix, after painting the model which, apart from providing a better appearance, will save a lot of awkward masking.
PICS 6 and 7. The Mk.V didn't have all of the cockpit side windows of the earlier Marks, and the extreme rear windows on each side were also deleted, so these were first blanked-off inside with thin plastic card, and then filled with 'Milliput' and the rivet lines added.
PICS 8 and 9. The resin 'plug' for the hole where the mid-upper turret and the 'Taboo Track' would have been, has been attached using CA adhesive. The Magna Models instructions suggest that this should be done by taping the fuselage halves together, and fitting the plug from below, through the bomb bay opening, gluing one side only. I found this very fiddly, and far from precise, as the resin part is quite thick, fairly heavy, and with minimal contact surface.
Instead, the part was fitted 'by eye', and took quite a bit of persuading, needing to be clamped in place, and CA 'fed' into the edges where contact was made with the fuselage.
I wasn't convinced as to the integrity of the bond, fearing the part might collapse into the fuselage when the filler is applied and sanded, so, as insurance against this risk, the kit's turret bin was cut down, fitted to its locating platform, and cemented in place to support the resin 'plug'.
PIC 10. The fit and alignment of the resin plug was checked by taping the fuselage halves together, and it appears to be reasonable. Once the fuselage is cemented together, the plugged aperture will be filled with 'Milliput' and sanded flush with the top surface of the fuselage.
Next stage involves finishing the minimal scratch-building in the cockpit area, painting this and the interior, and fitting the assembly, before joining the fuselage and moving on to the resin nose and tail parts. Hopefully, I'll get this completed tomorrow, and can then proceed with the remainder of the kit construction as per the Airfix instructions, but with the addition of resin carb intakes for the engines.