By Andy Bruce LONDON (Reuters) -Long-dated British government bonds sold off heavily on Wednesday to reach their lowest ebb in 20 years, after Bank of England Governor Andrew Bailey told pension funds they had just three days to fix liquidity problems. Twenty- and 30-year gilt yields spiked to their highest level since 2002, both exceeding 5.1% as the BoE insisted that its emergency bond market support will expire on Friday as originally announced. As of 1507 GMT yields on both gilts had settled back to 5.02% and 4.95% respectively, but still up around 10-15 basis points (bps) on the day. Addi…