Hi Simon,
Try an agricultural supplier, such as Countrywide Farmers, Bearly Mill, S-on-A. Ask for Silage sheet. Rolls come in various sizes ranging from £30 - 90. A bit of 200 micron sheet cut to size should last a long time I would have thought and when no longer fit for use cut another off the roll.
All the best with the new Parkrun,
Robert Barclay

Greetings all. Re: the plastic sheeting often put on floors at LDWA events: I am involved in setting up a parkrun in Stratford-upon-Avon and we want to allow muddy-shoed runners into the small pavilion. Is the plastic sheeting a prohibitive expense (parkrun is free to participants - it has some income, but not much), is it time-consuming to lay, and could it be repeatedly re-used if always in the same venue?

Advice welcome and received with thanks in advance