Adam, with regards to payments on account. (They are horrible) you only start paying it when your tax bill is over £1000. If it’s under that, then you’ll just pay the exact tax due and no more.
For me, I have to pay a big fat lump sum in jan, which I paid beginning of December to get it out the way. Then another (though smaller) lump sum in July.
The payments on account are ‘future payments’ towards your next years tax bill. So if you were to have a very bad year that next tax year, you could potentially get some of that ‘payment on account’ money back.
So your probably don’t have to worry about it at the mo, as your profit probably isn’t enough, yet..
Just bare it in mind, because the first year you fall into the payments on account bracket (larger tax bill than 1k) it really does cause some stress (if your not aware like I wasn’t) The first year it happened to me I wasn’t expecting to pay it, so I had to use savings to cover the cost. Needless to say I learnt from that for the next year!