Keep an eye on Swap Shop and I will post an offer of seeds when the time is right, usually in June. The seeds are spread by ants who lick off the sugar on them and then drop them in allsorts of odd places.
Mind they are not the only odd weeds in our lawn, how about primroses, cowslips, pansies, violets (ugh nasty things) potentilla warrenii and RAGWORT to mention but a few. Not much grass though.