GLA is currently open. UK gets the ash (at least directly from Iceland) when the wind at the appropriate level is a north-westerly. Forecast for the rest of the week is for this to change to westerly or south-westerly, so the ash will go north of Iceland away from the UK and most of Europe in general.

British Met Office is issuing a five day ash forecast every day at 12:00 GMT. They depend on a number of things so be cautious using them but they are some kind of a guide.