retro but quality amp for ESL 57's

Here is a link to a website that you may want to read:
http://www.geocities.com/drquad@pacbell.net/csramps.html

The 3020 works reasonably well with the Quads but you would be better off looking for the NAIM Nait 1. The NAD will be somewhat cheaper, of course.

NAD 3020 will work and was a popular choice when it first came out, worth a listen.

Although the 57s benefit from a low powered amp, they will be revealing of its inadequacies in the mid-range. When I got my first pair back in the early 70s, I used them temporarily with a Dyna Stereo 70, then a ubititous, cheap tube amp. I later used ARC tube amps in the 60-75 watt category- those were sweet in their day- but you don't really want to zap the speakers.
I would assume that in the UK, you have access to some interesting older products- I suspect Quad IIs are somewhat pricey, because of their collectability, but I don't know the market. Not sure, but I would also suspect Sugden make something low powered that is enjoyable to listen to; your ears will get better once you have owned 57's for a while, so the cheap throwaway amp may be no bargain if you get a hankering to hear what the speakers are capable of revealing.