Susan,
- holes in the awning rail, nice idea to get a length of new white strip and replace the part with holes in it, first filling the offending holes with some white Sikaflex
- holes in the side of the van, could you use the Sikaflex to stick some screw caps/covers, the sort often used on flat-pack furniture
- holes in the roof, when I removed the chimney flue on my previous van I cut a white disc out of a piece of 4mm acrylic, warmed it p in the oven and then formed it around a lump of wood I had planed to shape before sticking it over the large hole with Sikaflex
Sikaflex is the best "gunge" to use. It is a flrxible gap filling mastic/sealant/adhesive. 221 or 228 are I think the preferred choice, but very expensive. Go to Screwfix and use the general purpose Sikaflex they sell.
Colin