I had talktalk from day one with USB modem, so I've never had an essentials router.
With the FTTC I now have the router is a Huawei HG533 which is single band and quite low range.
Luckily I just finished my uni project on WAPs and have some dual-band Ruckus 7363's and Meru 320i's to play with.
The Ruckus have great range due to adaptive antenna arrays, but are expensive (£100+) and the Meru can be densely packed and are cheap for the WAP, (£25) but need a controller £250).
I know that's no real help to you. The cheapest thing to do is use old routers as WAPs. Maybe you can put them in ad-hoc mode so they don't need to be hard-wired together but I've never needed to do that so can't help a lot there.
In theory, theory and practice are identical.....in practice they aren't!