Federation of Small Businesses also signed the letter, but I'm sure they're actually nothing to do with "real" business that all agrees with New Judge ;P.
Also it's a bit misleading to state that "one in ten companies sells its goods or services to other EU countries" without also considering how big that 10%-ish of companies collectively is within the economy and how much of our GDP they account for. I don't know what that information is offhand, but it's rather a glaring omission