You could try locking your savings away, out of sight, out of mind and all that.
For example, many banks do a regular savings account where you can save £200 to £500 pm. They have different rules about whether you can get the money back, but it's not in an account that you can spend from, so it's harder to spend.
Also you could buy premium bonds. It's risk free and you can get your money back at any time, but I don't know how quick it comes back, or how to do it either. I have a few thousand in PBs and I know that if I needed the money, I could get it back in a few days/weeks, but in reality I'd have to read up or phone them to find out how, so it's a bit of a faff.
If you manage either of the above, and do build up a bigger lump sum, you could put it in a fixed savings account, so again, not easy to get back.
You say that you think 'fuck it' every time you see £500 in your savings account? But you already have quite a lot of spending money, if you are earning close to £2k pm and don't really have any outgoings. Focus on that £24k or certainly building up a decent sum.
Do you ever want to own a property? You are currently in the perfect position to save a deposit, which will be a lot harder if you move out and are paying rent. If you don't save a decent deposit now, you might be giving up the opportunity to own property for decades to come and you'll be more likely to be paying rent, ie paying off someone else's mortgage, not your own.