John Williamson wrote:

It's not as if DL are
particularly cheap, which would explain them saying they're not on the
comparison sites.

Actually for the last 14 years, DL or Privilege (who seem to be DL in
disguise) have either been the cheapest for me (by considerable margins)
or have matched or come within £5 of cheaper deals I've found on the
comparison websites and the specialist brokers ...