Britain has an excellent track record in space exploration
Britain has been involved in several important space exploration missions in recent years, including extensive participation in the Cassini-Huygens mission to Saturn. British astronomers designed some of the instruments on the Huygens probe, which landed on Saturn's largest moon, Titan. And British astronomers are members of several science teams for the Cassini orbiter itself.
This kind of investment in space exploration pays far larger scientific dividends, for a much smaller investment, than any hare-brained scheme to produce British astronauts. The only reason the government is interested in having astronauts is national willy-waving.