Before the van interior could be lined, the roof light had to be put in (£40 from the local caravan centre). This had two roles – a source of light, and ventilation for Harvey Dog or the cooking. It was pretty easy to fit – just mark out a 400mm square, drill 24mm holes in each corner, and then use a metal bladed jigsaw to join the dots. The roof gave a lot of vibration during cutting, and it was a daunting feat before-hand. Once in, it was sealed with black silicon and a couple of pieces of supporting timber were screwed to it from below (which were subsequently attached to the plywood panel lining).
The van was partially lined to waist height, but this was removed temporarily. Domestic insulation was then stuck on to the ceiling and walls using spray-on carpet adhesive (£4, B&Q). There was an insulation promotion on at B&Q and the synthetic material (made fom recycled pastic bottles) came in at under £10 (half price). Amdrorecommend a sheepswool lining, but this was cheaper and readily available.
Wiring for a 12v LED lighting system was also set in place, and then the 6mm ply sheeting was riveted back on to the steel frame (below the external bodywork). It cost around £15 for the additional plywood required. Ten 15mm holes were then cut for the LEDs. The lighting system was found in a bargain bin at B&Q for £20 (returned). Although it was 240v mains, it used a transformer and the LEDs actually work at 12v – so this was a much cheaper alternative than a setup from a campervan parts supplier.
The interior was finished with foam-backed charcoal chord carpet – £2.99/m from Carpet Right. Again, this was attached with spray-on adhesive. The carpet lining wasn’t installed until after the units had been built-in, though. There’s a diagram of the lining configuration on page 5 of this pdf.