[Lancashire Lad]

The price you were quoted was probably for Canon's own brand tubes.

However, since extension tubes have no optics, there should be no reason, other than brand loyalty, to purchase Canon branded tubes.

A set of 3 "Kenko TPL DG AF Extension Tubes for Canon EOS" tubes, with all control functions through connected, (so no loss of stop down /auto focus etc. etc.), should cost no more than £150.00 from any of the major high street retailers. (I've seen them as low as £85.00 online).

One downside is that there is a loss of light, (i.e. the amount of light that actually reaches the camera's sensor), when using tubes, which can be quite considerable if the 3 tubes are stacked together for maximum magnification.

If you do go down the extension tube route, I would recommend buying from a local retailer, and asking to try the tube set out with your particular camera and lens, so that you can actually see the magnification and any light loss problems you will be getting.

As for your other options, since you already have an EOS400, I would definitely go for a dedicted 1:1 macro lens rather than going down the G10 route, as you'd be paying over £300 for that, and it would still only give you 1:2 macro at best.

Regards,
Mike.