I started off on checkouts, I will give you my opinions, and that is, I did enjoy it, and loved the customer interaction, but I got a little bored, and thats why I started to learn self scan, kiosk and CSD before doing some running, which meant I had the variety, and you could pick up shifts and that on other areas of front end, so if ya want to once you have been there a while, get trained on other things, it helps.
As for the night pay, I dont know the exact amount to be fair, but £8.67ish rings a bell, be somewhere around that amount anyway, much better than day pay haha.
References.....could you ask a family friend that doesnt know you directly? or another professional....GP, etc? If not, they might accept the college/school reference if there is no one else, ring te store and ask for personel and see what they say.