Thanks everyone, the trailer is watertight, so that is good, and we have put a "moisture collector " in there to collect any water ( the sort you use in bathrooms. So just waiting for the sites to open and slightly warmer weather 😀
we store our tent in the garage - its damp in there but there is air circulating - it's been in there 5 years and no issues (wrapped in a tarp). We store windbreakers, portapotti, chairs etc in our trailer - we've not had problems with mould but then again our SIM etc goes in the loft as we dont like to take the risk. I think a lot of it is not packing too dense.
Youll be surprised how quickly the blue aero 360s fill up - they are effective but you might find silica gel sachets preferable (amazon, local hardware shop) - some you can recharge in the microwave so you dont need to keep buying them.
I have a Dax/Erde trailer with the GRP hardtop. Tent has been stored in the trailer for the last 8 or 9 years without any issues. Trailer is outside on a gravel base.
Late to this conversation- but we have always stored our bell in our trailer. The trailer has home made wood too and a fitted waterproof cover- never been a problem.