What sort did you get in the end? The Octagon, the half moon or the pillar?
There is a new one out called the AquaRattan as well, looks neat but completely unsuitable for fish with the water pounding down!
You can buy a unit to fit into the 4 in 1 filter you get with the Affinity Ponds
on the one you have now, it has a round blanking cap and the uv unit you can buy fits in there
its about £50 i think and makes a heck of a difference!!
Also, dont use an algae pad etc aimed for glass to clean the 'windows' on it, use one aimed at acrylic
no one considered this with ours and its so scratched up you cant see through any more! (best stop algae in first place!).
When it comes to winter, you will need to buy a pond heater, the fish will end up freezing, they arent designed to withstand winter without extra care. Personally, i would try building some kind of protective frame, even if just with some trellis and line it with plastic sheeting and bubblewrap or fleece or insulation padding.
Any pond or feature that is above ground is risky as the ground protects ponds that are sunk down and keeps them a little warmer lower down, without that protection.. its very risky.
Plan ahead now and it wont be a panicked rush come winter. You want to protect it from the snow and ice anyway, it will end up fading it wearing at it as with any garden furniture.