Undue hesitation is a minor, pulling out and causing someone to have to brake for you is a major. After your test you’ll soon learn that if your waiting for cars to signal correctly you’ll be sat there all day so you end up pulling out and upsetting people who are signalling. But for test definitely wait as long as you need to for a big enough gap.
Clipped kerbs - just start giving yourself more room on approach. Get your wheels on the white line or if you have to over the line. If you take too much space and realise you then don’t actually need it it’s easier to give the space back than it is to not allow enough room, realise at the last second and try and get some space when you’ve got traffic in the other lane. Always just take more than you think you need until you get the experience to judge it better.