I think you need to get a really good understanding of your finances, doubly important before your move in with your boyfriend.
Your take home pay should be about £2K per month, and your commitments, including an estimated £30 for water, and £300 towards your credit card every month, add up to £1,300. Potentially leaving you with £700 for food, transport and other personal costs.
When I was struggling to manage my money, I set up different bank accounts for different purposes. So as soon as my salary came in I transferred the money for bills to a different account (in your case that would be c£1,300K) and had all the bills paid by direct debit / standing order.
Next I set up a savings account and as soon as my salary came in I transferred £100 per month into savings. It might not seem a lot, but for me it was an important mindset, that I saved before I spent. I also knew that I was gradually building up money to cover unexpected costs / breakdowns.
From the rest, which should be about £600, I suggest you keep a meticulous note of exactly what you are spending that on - every single item, every single day. You say £40 per week on food, but what about the big expensive items like washing powder, cleaning products, sanitary products, moisturiser, birthday cards, wrapping paper...? The ocassional take away pizza, or the £5 contribution to a colleague's leaving present - include them all. And all your transport costs too. Even if you don't buy expensive clothes or have expensive salon treatments, you still need new shoes sometimes, and will need the ocassional haircut.
I worked it out over a 6 month period and there were all kinds of little, but mostly unavoidable, costs in there. I also found out where I had 'bad' spending habits - for me it was buying things from Amazon (things like shampoo or presents) and not factoring them into my overall spend. The £600 per month that you have for food etc, will fluctuate, some months are more expensive than others, that's why it's difficult to manage, and why you need to understand everything you buy weekly, monthy or quarterly.
I also kept a really close eye on the 'bills' account to make sure that my estimates were correct.
I can't tell you how good it made me feel to really be on top of all my spending and to understand where all of it was going. It didn't make me richer but it did make me feel less like things were out of my control.
If your credit card / loan is £1,500 then paying £300 each month could see that paid off in about 6 months too. Then you could put your refund money directly into savings. Wouldn't that make you feel good? If you pay that off, you could then put another £200 or so into your savings account.
I think it is particulalry important to work this all out now. When you move in with your boyfriend (or will he move in with you?) you need to know that your finances are fair right from the start. No point in you thinking you put £40 per week towards food if in really all the other personal and household items add up to twice that. It could be tempting to think that one rent or mortage means you save the rest, but who saves it? You or him? And will you save it or spend it?
Do you know what your boyfriend's approach to money is? Is he a saver or a spender, and does he have debt. All very unromantic, but essential. I think.