Thanks for the comments chaps.
I used the below from Amazon - I've spent the weekend at the Worth Valley, with model room sealed off at 18 Degrees and I'm pleased to report on brief inspection last night it appears to have set well this time.
In terms of prep work, I painted the area with cheap water based poster paint to a desired colour, it's crucial to remember it will look darker once the resin is applied. I then prepared the scenic area around it, sticking in reeds and flocking the bank. Other than that, mixing up the resin and pouring it in/spreading it about and trying to remove any air bubbles.
Hope this is of help