Note to self... (a lesson learned)
Do not deviate from my tried and tested suppliers! I have always used the same potting grit and never had an issue, but recently, whilst in a different nursery (in a hurry) I purchased some grit, which was not only very mucky (mine comes cleaned) but also I have noticed everywhere I have put it has developed some sort of weed that looks like miniature xmas trees! this is most annoying and time consuming having to keep yanking them out! Grrrrrr..