I’ve also found silicon remover is effective once you have pulled and scraped out the majority of sealant. But once clean as you say it’s vital to ensure the surfaces are chemically cleaned. Meths being very effective.When cleaning the old sealant off make sure you remove it from both surfaces, take bulk of it off with plastic scraper, then wet wipes, then white spirit, then finally to make sure there is no residue left use Metholated Spirit.
Time consuming but worth it.
Nice of you to come back and let us know how it went.So I took the window down, cleaned the hinge, cleaned the wall following Gagakev’s three pronged suggestion. It went great, glued the hinges back onto the wall, used matchsticks and wood glue to strengthen the screws until I realised I couldn’t fit the window because of the break light that sits right above the hinges in a protuberance that prevents the window from being fitted onto the the hinges. So, I took everything off, cleaned all the glue which had hardened nicely and fitted the hinges directly onto the window and then the whole lot onto the caravan.
Thanks for all your help, I now have a window I can use - which is great because that sunny weather sure heats up the caravan!