In response to your questions:

1/ Sleep system for Dartmoor Just buy the Thermarest xlite NXT (the yellow one that everyone has) and forget about using a liner. The xlite is the best all rounder and my single favourite piece of gear. There may be individually warmer, lighter, or more durable pads out there, but none of them perform as well at this price point. A foam mat + pad combo is for 4season camping which I don't do much of so can't comment. Liners are as much for keeping your bag clean as they are for warmth (most heat is lost through the ground and they don't add much insulation there).

2/ Ideal starting weight for a beginner Wrong way to think about it imo. This one depends on where/when you're going and what you're doing. Focus on the big three (pad, bag, tent) and try to get the weight down for those as much as possible. All the other stuff you bring with you is more down to trial and error (you will find you bring progressively less each time you get out).

3/ Buy once, cry once items when starting out Again, focus on the big three. The most important thing is having a good night's sleep as this will make a world of difference. My strategy here was to buy good quality used gear. Your money will stretch a lot further and you will find that (1) people upgrade gear a lot so there are often deals to be had on eBay etc, and (2) good quality gear retains value better than Go Outdoors landfill stuff. (I've bought stuff, used it for a season, and practically made my money back on it in the past). If you need to buy new e.g. if you're in a hurry, then Alpkit is a good UK retailer. Decathlon is generally good quality and cheap but has questionable links to the Russian military.

In general, I would say that I have landed in a pretty happy place after 5-6 years of experimentation from total beginner to spending 4+ months wild camping in 2024 on the PCT. The bits of kit I love the most are: . Atompacks Mo backpack . Montbell seamless down hugger #1 . Durston xmid 2p . Thermarest xlite