The weather report says be raining when we go away this weekend, so I just popped onto Amazon and looked for a sealer for the tent.
After reading all the reviews, I decided on Atsko Silicone Water-Guard. The other products available sounded pretty dodgy, so I opted for this one.
It is very easy to apply. It is quite smelly, but after a few hours, the smell will fly away and you are left with a waterproof layer. Watch this space for further updates.