Hi Ruby,
our little playgroup is having similar problems, it is on the primary school site - but the primary school nursery class has started taking in children termly so they are all jumping ship the term after they are 3.
We have discussed them changing the midweek session from a 2year old with parents session to a mother and Baby group, therefore attracting parents much much earlier.
Also having the option of a lunch club/breakfast club.
opening during school holidays/ using the building during school holidays for Holiday clubs that could be charged at a more commercial rate.
We have found that alot more mothers in our area have been going back to work and therefore needing to pay for commercial nursery times.
I think we need to address the parent helper.cleaner issue that we have.. most of the parents who move at 3 years old move because they don't want to do these things any more.
Sorry if these aren't any use - it is just what we are going through at the mo.