Lupins are herbaceous (means they die back completely in winter) perennials and will grow again next year. Cut off the flowering stems if you haven't already done so. I would let the leaves die back naturally though I suspect a lot of folk will cut those off too my view is that just like bulbs the leaves keep feeding the roots until they die.

Sweet peas it depends whether you have the normal annual sweet pea or the perennial one as to whether they will grow again next year.

If your sweetpeas were the fragrant sort, then cut the vines off at the base and remove them. That's it for this year. If you happened to leave any seedpods on the vines, you could collect the seeds and plant them in pots (under glass) ready to plant out in the spring. I'm sowing mine tomorrow!