I have used free municipal compost for a few years now in York, and it has been very good. This year i have a had a problem with it. I used some to mix in to make growing soil for some tomato plants growing in buckets. The tomato plants were fine when they went into the buckets, but i noticed that the new growth at the top and in the leaf axils was green but small stunted and twisted. I am guessing that this is the result of weedkiller remaining in the compost. Probably caused by someone putting grass cuttings in their green bin that has been treated with weed and feed. Be aware that this can happen with municipal compost.