You shouldn't cut them back. Just let the foliage die off naturally so that the bulb can build up strength for next year. A bit of feeding before the leaves die helps too. Once the leaves have gone you can dig up the bulbs if you want to and store over the summer to replant in autumn, but I always leave mine in the ground.

I leave mine in the ground and leave the foliage on for at least 6 weeks, I feed just as they finish flowering, that's the same where ever you live in the UK. But lifting may be different for you in the NE? here in the SE I leave them in the ground.

We leave ours in the ground all year round.