As RichardV6 states :
Paul although you have changed the 6 pin wiper delay relay please note that MMC appear to use the standard 5 pin relay base connector with a sixth connection added for the narrower "I" pin. This is the one that accepts the intermittent trigger so worth checking this connection is good as a replaced relay could still leave no connection here and it's a known issue!
I discovered this very issue when I had no intermittent wiper function. If you have removed the relay you must ensure the exrra 6th pin and wire are connected manually.
