My take on it:

In reply to a post by Woolwich:

According to Plusnet, Openreach will bring two devices to connect.

OR will bring 1 device, the modem. PN will post 1 device, the cable/fibre router, to arrive before the OR visit.

Other ISPs will either supply the router free, allow you to buy 1 from them or let you use your own router.

In reply to a post by kasg:

Anything sold as a "cable router" should work.

Brilliant, thanks for that. Very useful. I've always used Draytek ADSL modem/routers in the past, I'm sure they'll have something suitable!

In reply to a post by Woolwich:

You're right, they didn't! I was speed reading their FAQs where there's a graphic (can't find the page now) showing the two devices and describing the installation. But if I read carefully they do say they send the modem before the OR installer comes.

I stand corrected!

Not quite, Plus Net will send the router in advance not the modem, the installation engineer brings the modem. Probably a typo, but you could do with editing your post for future reference.

Typo corrected!

In reply to a post by Woolwich:

Brilliant, thanks for that. Very useful. I've always used Draytek ADSL modem/routers in the past, I'm sure they'll have something suitable!

Plusnet uses a modified Thomson 585, it is a ADLS modem/router with a different firmware and one of the lan connections modified to to act as a wan.

It is a awful bit of kit, the wi-fi is about as useful two tins either end of a bit of string being used as a phone.