Don't quite know what you would be planning to do with that scart extender but I highly doubt you will get any sort of satisfactory results using that contraption. For one it has no switching circuitry.
In terms of 5 port switches, the Carrefour ones - like this:
http://www.ebay.com/itm/SCART-BOX-5...227959?hash=item35f78928f7:g:Nk4AAOSwu4BVpXQh - are IMHO currently the best bet, given that the Bandridge 5 slot is no longer available.
I have written a little bit about the 3 slot version of this switch in this thread and after using it for some time I can say that:
- the switching circuitry is fine, it isolates the selected input from the other inputs, there is no interference etc. so the basics are covered.
- the scart plug on the output cable side was at least in the case of my switch of a particularly crappy quality - the pins were misaligned and the plug was difficult to insert in a scart socket without bending anything. I have since threw the stock plug in the garbage and just soldered in a replacement male scart plug. Equally well, you can dispose of the plug and rewire the output side for BNC.
- the female scart input connectors on the switch side are so-so: when using certain scart plugs it is not as snug connection as one would hope for or as is the case in e.g. the Bandridge switch. This is not really anything too dramatic, but if you are often changing cables etc. you may find that every so often you need to reaffirm that the scart plugs are fully seated in the switch.