What bed/mattress should I go for?

Hi,
Following up to previous advice I've initially been given by yourselves, I would like further recommendation please to help facilitate and clarify few things before making a purchase.
I'm in the market for a King size bed/divan and my budget is £1200. I’m a traditional side sleeper, sleeping on my left side/slightly to the front and generally do not move from that position. I am upgrading from a single slatted wooden bed on a very old mattress which I believe is open coil, where I can feel all the lumps and bumps!! I weigh around 62kg and I'm 6ft. I have tried many beds and extensively research around your website. I have now narrowed it down to three or four beds but still cannot make an informed decision about what would be best.
Currently these are between Origins Comfort 1000/1500 you offer and the bespoke grandeur and splendour divan bed sets from bensons. I did like the feel of both the bespoke bed sets and it was suggested by bensons having used their comfort station that medium firm would best support me. As these have an option with a sprung base, What can you tell me about sprung bases? Would I be looking for firmer or softer base and what difference would this make to me? I am tempted to buy and try out the comfort 1000/1500 but given my budget I could probably get more than standard polyester upholstery layers? I did ask Bensons how much weight of the Wool, Silk and Cashmere were in the aforementioned sets but they were unable to provide me that. Given my weight and sleeping position would this be deemed to make enough of a significant impact in feel and comfort?
It was also suggested to me to go for the standard divan base augmenting the comfort 1000 with your Laygel 7.5 cm topper to provide the best overall feel for me. However I see you sell this at a quite steep price. Could you recommend any alternative toppers I could try with that Mattress or could I go without? If I did choose to go with all three of your products and I'd didn't get on with it, would you refund the price of the topper included?
I am tempted to buy comfort 1000 or 1500, but I am getting confused as to what the best bed/matress for my budget?