Last year (2011) we watched 10 mini caterpillars transform into painted lady butterflies in our kitchen.
It was truly amazing to see the whole life-cycle.
Although I hesitate to recommend stuff ‘cos our experience could have ben a fluke, you can get the kit here: https://www.insectlore.co.uk
The link above is a seal for 10 caterpillars rather than the pack on Amazon which is 5 caterpillars.
What we experienced last year really was worth the £20.
This year we have just taken delivery of 25 silkworm eggs. Watch this space for an update in a few weeks.