Paines Plough have an open submissions policy, here are all the details:
Not only do we accept unsolicited scripts, we love receiving them. We read every play we’re sent and consider it for production.
If you think we’ll like your play, upload it using the form on our website. Then within ten weeks we’ll let you know whether we want to produce it or not.
Please note that when George and James are in production it can take a little longer for us to get back to you. We can only accept scripts by form so please don’t send us hard copies – we’re trying to save trees.
We do workshops all over the country too, so let us know where you’re based and we’ll get in touch when we’re local.
Here’s a link to the page on the site
Source: direct contact.