in the end i contacted a boiler engineer, recommended from a friend at work, who has had a look at clock and diverter and has happened to get a wee electric shock off the casing. he thinks it needs a new wiring loom and possible replacement diverter
this could get pricey, as he suggests that if the parts cost £200-300 then i would be better off just getting a new boiler
How do gas fitters find combi's so hard to work on.
Definately get a second opinion.