Somebody told me that the band which played with Ian Dury - The Blockheads - have, before being The Blockheads, played with Steve Harley
Sounds quiet strange to me.
Anybody here to tell me if it's right or wrong ?

I've never heard that before. I think I'm correct in saying that Steve filled in for Ian Dury for a benefit concert when Ian was too ill to attend and so he did front the Blockheads for a one off concert. Perhaps that's what you friend is thinking of?

Seem to have a vague memory of Steve being lined up to sing with the Blockheads at a tribute concert around July 2000 at the Brixton Academy in London,about four months after Ian Dury passed away.
Do not think Steve did this but people such as Robbie Williams,Kirsty Macoll,Mick Jones of the Clash and Madness,were on stage that night.
There has since been a tribute album released called 'Brand new boots and panties' featuring most of the above plus Paul McCartney,Billy Bragg,Cerys Matthews(Catatonia),and Shane McGowan of the Pogues.
For a stage show which had a west end run a couple of years ago the part of Ian Dury was played by comedian Phil Jupitus,for which he gained rave reviews apparently.

Thanks guys. So if I understood well, he was going to but he eventuelly did not, right ?

www.harleyfanzone.com/Ray/Road/Road_61.html

I checked with Steve in Australia last night - he flies home today - and he confirms that he and he fullrock band stood in for an Ian Dury and The Blockheads date in the west of England, he thinks near the Wales border, several years ago.
Ian Dury was very ill and the band cancelled. Steve remembers his band learnt Hit Me With Your Rhythm Stick, although he had to read from a lyric crib sheet!. But Steve has vener sung with the Blockheads.
That should clear it up!