Check whether your contract ends on the last day before the hols, or the day before school goes back. You might find you are paid for the hols.
If you are paid on a supply basis, then they work it out differently. Salary divided by 195 (number of days worked). This is how they make sure a supply teacher can earn the same as a salaried teacher (wages/12 for each month) if they work the whole year.
If you are on a short term contract, then the school can benefit because they can end your contract before the holiday and then not pay anyone for that holiday.
As far as pay rise is concerned - it looks like you've worked about 22-23 weeks. (Depending on whether you are on salaried contract or supply - not sure whether the holidays will count if you are on supply basis) so if you can secure supply in the same authority and work part of another 4 weeks or so, then you can clock up the 26 weeks pay you need.
If they decide to work it out as the 8 days that you have worked, then you'll be paid like a supply teacher 8 lots of 1/195th of your wage. I know when I was deducted a day's pay when there was a strike it looked like a lot more of 1/30th of my months salary. There's a bit of hope there.
On the plus side, you are still NQT so nice and cheap - and you have a term and a half under your belt so have a bit of experience. Get your face into lots of local schools and put your name down for supply. I know a lot of schools go through agencies, but there are always some who prefer not to.