Went to run it up today as it hasn't been driven properly for two weeks, it started during the week. The car won't crank over, the relays go mad and the boost gauge goes mad clicking. The headlights just about work.

Does this sound like the battery?

 

Is it a blob eye? Mine did that after sitting for a couple of weeks when i was selling it. Fitted a new battery and thought it was ok. Guy got 20 miles down the road and car died .........
It was the alternator that had packed in so i would test that first

 

yep sounds like the battery to me,suggest if you can trickle charge it and get it tested ,would you have a voltmeter handy to check its voltage first

 

update,

after half pushing/towing it up my steep drive, bump started it and it started, getting a new battery tomorrow, are halfords any good, I have a trade card.