It is hard at first, I feel for you both! It is a big step, but dont worry, he won't resent you and he will still trust you! One day you will even be a bit peeved when he doesn't want to go home!
I am 2 months down the line with DS2 (21mo), and it has been up and down. We did a 2 week induction period (I am abroad-this is non-negociable at this crèche). For the first week I stayed with him, basically he ignored me and had a whale of a time. The second week each day I had to leave him for a bit longer-10 mins, 30, 1h, 1h30 etc.
And it was a nightmare! Ended up doing a 3rd week like that, with lots of tears on Ds's part. It has very very gradually improved and now he goes in without crying (not jumping for joy either though), and enjoys his time there (4 mornings, 1 day until 4pm).
Things the staff did to help: Taking him straight into their arms for a quick cuddle on arrival, and distracting him so he didn't have to watch me leave. Keep goodbyes breezy and short, remind him that Mummy will be back later.
Distracting to ward off/stop crying during the day. Songs, looking at stuff, painting, music, dancing...
I don't know much about UK nurseries, so maybe someone else can help you there!