So - it turned out to be two things...

1. I'd bent a steering arm, this meant every time I took a corner in one particular direction it was trying to do its own thing
2. Driving it home like this must of opened up the gap that the track rod end slots in to ontop of the hub.

A new (old) steering arm and a whack with a hammer to close up the gap on the top of the hub sorted it all out. Ace!

Can you buy stronger steering arms?

"gap at the top of the hub" if the steering arm being the short arm thats bolted to the top if the swivel housing then it should be in tight with 10.9 bolts. to the correct toeque

Trouble in your case the bolts will be over stressed, UK racers often weld the arm in or you can do as we do and tap out the hub to M8 and fit allen head 12.9 bolts which can be horsed up good and tight.The tapping can be done with the bearing in situ if you are careful and have a good bottom tap. The bolts need to be cut to the exact length and i buy 40mm ones as the plain shanked area is the right length for the longer bolt.You may have to increase the diameter in the arm to give you a working clrarance. The actual arm can have a web welded in to the curved section but bear in mind that welding to any steering component is a MOT fail in the UK

SubaruPete posted a link to 12.9 hex head bolts which could use the locking tabs although ive never had any allen head come loose in the last 10 years

the long steering arms the bits from the centre of the rack to the levers can be beefed up by slipping a piece of steel tubing of the correct diameter , jam it tight on the bend inboard and use a lock nut on the threaded end , welding has caused bending.

if all this sounds too tech Pete should be able to sort you out and the "Belgian Arms" should help with the extra power.

Sean,

Thanks, excellent top tip about the steel tube and lock nut over the steering arm - I'll get on that.

Ahh no the track rod ends were fine but the opening that one of these sits into had opened up - it was all torqued down correctly before, seems fine now I've carefully bashed it back a little tighter. And yes, I changed the bolts into the hubs afterwards as I've had two of these shear on me when I've been driving... it scared the crap out of me.
I'll consider M8 in the future if this becomes a re-occuring theme.

Ha yes, I've got a shopping list I'm compiling for it's next return to Sparrow Hq.

Cheers

I know this comment is a little bit late but, We had this "juddering " problem too. We thought that it might be the same culprits as on Fritz' green car... We checked all the steering, fitted new king pin one the driver's side (wobbly side) and checked the track rod ends which had slight play, but we thought that it wouldn't really effect it. We put it back together and tested it.... The bloody thing still juddered!!

It turned out that the drive shaft castle nut had become loose after it had all settled in... We found this when we wobbled the wheel by hand. One tightened it hasn't rattled/wobbled/flapped/juddered since!!