Hi Pat, good to see the van has safely arrived.
Now it's had basic wash down you sound like you have assessed it.
- The green algae stuff I'd treat in the say way I do that which forms on the window rubbers of my car. One part bleach to 4 parts water, applied with a small nailbrush or toothbrush. Leave 24hrs and rinse off. Repeat if needed.
- Roof, both pop-top and the bit above awning rail and the pop-top. You can buy expensive GRP polish/reviver, but I've never bothered. It sounds as if your van was similar to our last van that had been outside stored for 5 years. I used T-Cut and then Autoglym car polish. MER is also excellent and favoured by some owners. This brought the roof back nicely. I usually polish the roof twice a year. Once at the start of the season when the cover comes off and the other towards the end, so its still fairly slippy when the winter cover goes on.
- For the outside paintwork you do need to be careful as the paint is very thin. I car shampoo followed by the wax polish will do 99% of your needs. Any tar spots or streaks I do with a spot of Meths or white spirit.
- if you use the search facility you will find lots of advice on cleaning up the white trim. Do not rub to hard or the body paintwork as you can go through the paintwork.
- If you see mastic oozing out of the awning rail then do not pull it out. It will continue to ooze for many years. Best thing is a dampened white spirit rag wiped over it, cut through the ooze with an old credit card and roll it up [like a ball of snot] before wiping the area clean with a clean white spirit dampened rag. Re-polish the surrounding area just to get a shine back onto the bodywork.

Colin

I weigh 82kg and I crawl across the pop top roof, but would not do this on the normal roof area at the back of the van. I have a couple of times stood on the roof, but it is not something I would advocate.

Colin

Philip, nothing personal, first question are you smooth or dimpled. If smooth then Fiat Bianco White is I believe the colour. For dimples I had Lowdhams of Nottingham supply me with a genuine touch up brush paint. I have used this on a couple of stone dings and in two places where I was a bit vigorous cleaning around the waist rail and thinned the paint.
As regards silicon, it really should never go anywhere near a paint finish. If you tried to paint over it the paint will not stick.

Colin

Oh, In my ignorance I thought I was OK using my AutoGlym.

Cheers - Colin