I wouldn't worry about it now - its autumn,the growing season's over and your alstromeria will be disappearing below ground as the season progresses.

Thanks for this, I was wondering myself if they were just switching off for the year ...and I don't want to be greedy...but other newer clumps ( I bought some more because I was so pleased with the first lot!) are still flowering well and putting up strong new shoots. Alstromeria are a new plant to me so I'm feeling my way on how to treat them. I've read that I shouldn't cut back the finished flowering stems, but pull them off instead. That seems to work OK, but I'm not sure how they like to be treated in the autumn. Do I yank off all the stems or just leave the foliage to die down?

Ah well, that depends on how tidy you like your garden to look - they should be mulched for winter to give them some protection, but if you let the leaves die back naturally, they provide some protection for the roots by acting like a mulch. Wherever possible, I cut nothing back for winter, just clearing away dead stuff in early spring instead - better for wildlife too, including insects.