Credit score help

Don't pay attention to the score. Pay attention to maintaining the best credit files that you can. The most important thing is to always pay things on time. If every account reports a status 0 (green tick) each month then you are fine.
With regard to the credit card that you have, always pay in full every month. Ideally set up a direct debit to ensure that no payment will ever be late or missed so long as you have sufficient available funds in your current account.
Unfortunately, utilisation is not what you suggest, where you spend the limit and pay it all back so they know you can afford it Spending a lot and repaying it so they can see that you can afford it works very well for increasing the spending power of an Amex charge card but in this sense utilisation refers to the % of available credit that you are using, the idea being that the greater the % the more reliant on credit you are or the more desperate for credit that you are. A high utilisation % can also indicate high levels of debt. In the case of cards with higher credit limits, individuals who habitually spend larger amounts and pay their cards in full each month are not concerned as they have the credit limit to support it. So with a £200 credit limit. if the balance of the card account is £150 you will have 75% utilisation. With a credit limit of £2000 a similar spend would only be 7.5% utilisation. The optimum utilisation figure is apparently 10%. You should normally keep utilisation down to about 30%
This is where things begin to be difficult. You have been given what for all practical purposes is a ridiculously low credit limit. As the direct debit will not be taken until the payment due date, by the time the direct debit is credited to your account it will soon be time for the next statement to be generated. Therefore, even at full utilisation, you would be unable to spend more than about £100 per-month.
So what to do?
Others may well suggest differently, but in your place I think I would go with a higher spend option, spend say £150-175 wait for the statement, repay immediately after the statement was generated then spend another £150-175 the next month and repeat. Pay attention to your issuers policy regarding direct debits and payments made before the direct debit is taken. If your issuer does not take the direct debit once payment has already been made, then set up a full balance direct debit. If your issuer takes the direct debit regardless of any payment made, then set up a minimum payment direct debit and make an earlier payment for the difference between the statement balance and the minimum payment.