Believe it or not part of the reason every summer is that the people in the USA all go on holiday and buy more fuel and hence the price goes up.
A feature of the "global economy" is that that actually affects everywhere else. As it is only just July this is probably going to cause more rises in the next week or so, so I am not sure why the recent increases have happened.
When vat went down in December the govt kindly increased duty to keep the price the same
This December when vat goes back up the govt will reduce the duty to keep the price the same (surely !)