From what i've read you need both carbohydrate and protein pretty quick after a ride. Most recovery drinks are based on chemicals/ingredients isolated from milk products (whey protein). So there is common sense (and scientific study) in thinking that perhaps milk might be a good, cheap idea.
Recovery stuff is very expensive if you are using it regularly.
Personally I use SIS rego, chocolate if I'm out. If I'm riding back to my door I'll have a large glass of milk, peanut butter sandwhich and a nap. Then I'll have a decent meal with plenty of protein and a decent nights sleep.
I would say there isn't much in the various different offerings so get some sachets and see what works for you in terms of flavour and stomach* and go with that.
* I found some make me feel a bit sick and others give me terrible wind which doesn't make me popular on the drive home.
Zipvit have a trial pack for £4, discount suppliments do a High 5 trial for £3. Your local shop sells milk. As for protein barsI like the "wholefood 9 bars". Not sports stuff but packed with protein from decent sources.
And finally. When watchin the tour last year it was noticeable tha riders not going to be involved in the final sprint/break and just coming in in the peleton were switching to recovery drinks before the end of the ride.
Not easy to do on your own but if you are out for a really long time might be worth eating a protein bar of the last 30 minutes.