are they cream with a brown head? if yes then they are vine weevil grubs. they may be other insect larva but this is the most likely; any chance of a photo charlie?

The adults will have laid their eggs in the compost and when they hatch they eat the roots of the plants. they then pupate in the soil and emerge as an adult in the spring.

They love peat based compost so why not change to a non peat based one?

thank you for your advice& tips happy &healthy new year to you all charlie.

I have read that Amillatox can be used but will only kill the eggs that are near the surface. I have tried to find out whether Amillatox will burn any plants that it comes into contact with but have had no success. Miraclegrow compost could be bought with an anti-vine weevil chemical but haven't seen it for sale lately. Camomile's suggestion of using John Innes soil-based compost seems the most logical way to go.

Just make sure it is a peat free JI Compost as the standard one still has peat in it.
Provado will kill the grubs if you do not mind chemicals.
Nematodes control them when the soil is warm.
The compost with insecticide in it may probably have been withdrawn as the chemical was Suscon Green which is an organo-phosphate poison and not very nice.
Can give you one tip which is good for bulbs and corms which need to be buried in a plant pot. Fill the pot to about half full with a good rich compost with a little added long term slow release fertiliser. Place said corms and bulbs on the surface and then cover with 5 to 7 mm grit. There should be at least 2 inches of grit above the bulbs. The adult cannot smell the soil and so does not lay her eggs. Also keeps the bulbs from rotting.