It does help to start seeing things you take for granted as luxuries you are choosing. I'm not talking luxuries vs someone who is struggling but simply luxuries vs a "normal" baseline.
For example - you mentioned heating and food. Heating is not IMO a luxury, it's necessary for health and to keep most houses from becoming damp/pipes freezing, but if you choose to keep your house at say 25 degrees or higher, then that is a luxury choice you are making.
Food isn't a luxury, and I don't think you need to be meal planning down to the penny unless forced to, but if you're making choices like - buying (esp. higher end) convenience foods, regularly including alcohol in your weekly shop, mainly choosing brands, having a lot of "extras" like snacks or foodie ingredients, following a special diet for lifestyle not necessary reasons - these are luxuries you are choosing to spend more on.
Most people drive a car, but you have a choice whether you spend £12k or £20k or £40k+ - even on finance these are going to affect your budget over time.
If you have a mortgage you've been able to put forward a deposit which is a huge sticking point for many people my age (30) and younger so you've done well there, I do think that's a luxury/lifestyle thing these days.
But yes £700 is quite a lot to have for socialising, entertainment, food, clothing, emergencies! It's most likely the emergencies and food which is getting you, though, so it would be a good idea to separate these out from that "general pot". For example, put £1-200 into a savings account every month to cover emergencies, rather than letting it sneak into general spending if you don't have one one month, track/check your food shopping and the rest for social, entertainment, clothing, etc. Get onto a debt plan to minimise that and you'll soon clear £7k which will free up more spare money, and check those fixed bills to see if there's anything you're overpaying for or don't really need.