To cut a long story short, we will make as many boards as you want provided you are happy to pay our price.
Another way of looking at it, is that there are suppliers both in the U.K. and world-wide who can make top quality boards. As the quantities go up and the lead times go out, the prices some of these charge are so competitive that many who have tried to match them have ended up going into liquidation. We don't intend to make the same mistake.
Taking single euro size pcbs as an example, we regularly make batches of hundreds off. We make far more batches of tens, twenties, and fifties, etc., because our prices are much more cost effective for such quantities. Customers who value peace of mind, however, and who don't mind paying a little extra to get known good boards delivered on time will also use us for the larger quantities.
Yet another way of looking at it can be summed up in the old adage: "For the most part, you get what you pay for".