Chris Davies wrote:[color=blue]
> I'm interested in an ATA with two internal extension ports and one
> (analogue) PSTN connection. I'd like one of the internal ports always to
> default to the PSTN line, but allow routing via at least one SIP provider
> given some particular key sequence prefix (e.g. #001*, or whatever). The
> other should default to one of the SIP providers, but allow routing via
> either PSTN or any of the other SIP provders given some particular key
> sequence prefix.
>
> Pricing would ideally be towards the lower end of the market but
> definitely sub-£100.
>
> Any suggestions, please?[/color]

You get what you pay for (more or less).

Around the 100 squid mark is the Fritz!box (with vat and delivery)
which, configured correctly, will do all you want.

At about half that price, with some limitations, the grandstream 386
ATA doesn't do exactly what you want, but can work around it-ish. It
doesn't default to PSTN on either port, though, with a dialled prefix,
your PSTN can be used. Each port would need its own SIP
provider/account as there is no dial plan to choose SIP provider when
dialling - whereas on the fritzbox, I believe, you can dial out from
port 1 using account 1 or 2 etc.