Yes, but managed entirely by BTw.

From what I read here, I would say that PN's 1st line support is far superior.

However OP did ask for cheap and EE can be cheaper than PN. Depends how necessary support is to OP.

But different routing out of the BT Cloud.

Another possibility is one of the TalkTalk Business Wholesael providers, who use the TalkTalk DSLAM but non-TalkTalk backhaul. Vivaciti and xilo spring to mind. Aquiss?

Not sure on the pricing for such though. May be OK with the 100GB rather than unlimited.

In reply to a post by XRaySpeX:

However OP did ask for cheap and EE can be cheaper than PN.

The OP is after four different suppliers, over four different voice lines (as I type this I realise the stupidity of stating that four ADSL connections requires four voice lines, yet I'm continuing to type ).
There are normally only three reasons for this (higher download speed required, higher upload speed required, redundancy) and all of these, coupled with a requirement for cheapness, probably require a certain amount of give & take between cheapness and quality of connection.

In reply to a post by RobertoS:

Have a look at Plusnet, where unlimited is either £9.99pm or £12.99pm depending on Market area of the premises.

Shouldn't that be:
unlimited is either £9.99pm or £16.99pm depending on Market area of the premises?

However there is a current offer till 7 Feb of either £4.99pm or £8.49pm when you take their home phone.

I'm a bit surprised at the specification to be honest. But that's what the OP wants. If he wants to achieve load-balancing across all four, or even two pairs of two, I would imagine there will be a hairy setup and maintenance task. But not my subject, so maybe it's easy if you're used to it.

In reply to a post by adebov:

The OP is after four different suppliers

And I'm suggesting one of them. Just answering the OP Q!

In reply to a post by RobertoS:

. If he wants to achieve load-balancing across all four, or even two pairs of two, I would imagine there will be a hairy setup and maintenance task. But not my subject, so maybe it's easy if you're used to it.

It may even end up being hardware dependent.
If one, or more, of the DSL suppliers insist on providing ADSL routers which cannot (or cannot easily) be set to bridge mode, the OP may struggle with load-balancing hardware.
In this case something more ingenious would be called for.
Ever tried overriding that sort of thing using the clunky user interface in something like the HomeHub, or the kiddy cartoon user interface in a Speedtouch/Thomson ADSL router?

Yes. Fixed, thanks.

My eyes jumped up a block instead of a line in this section after typing the £9.99 and going back for the Market 1 price.

Well, in the office we have three lines, normally requests are NAT-ed out to one or the other depending on what they are (e.g. VOIP goes via 1 line so the rest of the traffic doesn't make the sales team complain about voice quality). But if a line is down I can quickly change what goes to which line. Or could have a round-robin arrangement (in fact we have that on the two non-VOIP lines at present).
Not really hard to maintain, and people have been known to be able to follow my simple instruction to change which line does what when I was out on the hills and they had a line fault.
If gets a bit more complicated because we have incoming connections too, but nothing really difficult.
But I'm sure the OP have decided how they are using the lines, and the request is who to get them from.