Agree with that. 20/5 is a sensible option for a slower line or for people that don't stream content as much as others. 5 Meg upload would be a nice increase on the 1 Meg too.
To be honest, being on 11 / 1 (ADSL2+), I find it fine most of the time. I don't need HD quality streams, but it would be nice to have say 15 Meg and 3-5 Meg uploads for when I do the odd big upload.
In that sense, your 'quarter of download' rule would give me 2.75 Meg upload on my current D/L speeds. I would love that.
Now if Plusnet would increase their monthly usage limits to 100 Gig on their legacy products, that would be perfect.