Will be looking for one at Stoneleigh, but not too sure which would be best.

Plan to fit it in top panel, covering boot & tank space. Have noted various comments on this section of Forum re this installation.

So, which version would you recommend? And from which supplier?

Bear in mind IVA requirement for captive filler cap. Also lead-free restrictor ( not that you can buy leaded anywhere ).

For IVA it must:

Have a positive locking action - ie, something to stop it falling off when you hit a bump, some inspectors interpret this to being a security lock.

Have a lead restrictor fitted (unless you run leaded.)

Must be secured to the vehicle, or incorporate a lock, that when unlocked, does not allow the key to be removed.

I haven't found an aero style filler that meets all of those out the box, so I used some chain from a sink to tether it. I have some pictures and a write up here

It seems the ones to get are the flush fit, with the neck included. Otherwise, the "much less expensive" bike caps, don't have this, and you either need to buy/make/scrounge one, making the price fairly equal. However, that said, I don't see why an old filler neck from any old car wouldn't work. Maybe someone can enlighten us on this.

Thanks for the feedback, guys, and thanks also to David for those photos.

Have noted the IVA points, and will be testing a few examples at Stoneleigh.