In UK Pool rules, what happens if both players are on black and a player deliberately taps the white 1cm forward into nothing?
As I play, this is a foul but as the next player is on black they do not get 2 shots, however this tactic was employed to have the black ball moved by the player not committing the foul to move the black from a tricky position.
TL;DR: you're not playing under any even reasonably recent version of the English Pool Association rules, so we can't answer the question.
Under current English Pool Association rules (which are the same as the World Eight Ball Pool Association Rules), a foul when the black is "on" still results in the opponent receiving two visits to the table. A foul results in a loss of frame only if the black ball is potted.
Under the old EPA rules (pre-2009),
A player who clearly fails to make any attempt to play a ball of their own group will lose the game.
but this rule does not exist in the current rules. (Note that "game" in this context means "frame" rather than "match").
Neither of these rule sets (nor the 2009-2014 rules) include the stipulation that a player on the black does not receive two visits, so you're going to have to ask your tournament organiser.
