HELP - any shortbread experts around?

[sparklyshoos]

I've made a Jamie shortbread recipe a few times and it's worked out great - this time though it's all crumbly and won't come together when I try and roll it out - any syggestions??? (250g butter, 125g caster sugar, 250g p.flour 125gcornflour)

i'd add a bit more butter or a drop of milk but I supose you've worked it out by now?