Restricted Areas
 

Just confirm to me that I my understanding is correct.
A restricted area "R312/2.1"
The Upper vertical limit AMSL is 2100, i.e. You may fly at an altitude over 2100 and not infringe the restriction.
Forgive me if I appear thick but I have been reading the AIS all evening and cant make head nor tails of it!!!

No.
If you fly at 2100ft, and the upper limit is 2100ft, you will be infringing the restricted area.

If you fly at 2101ft you will not.

Bear in mind that, if you overfly a danger area at 1ft above the notified restricted altitude there's a very good cahnce no one will notice and you'll be safe from whatever is going on there because whoever runs the area has decided that at that level you'll never come into conflict with whatever it is that's going on below.
If you overfly a restricted area 1ft above the notified level, it will be difficult for whoever has established the area exactly what level you are at, you will be considered a threat, and counter measures are highly likely to be taken.

It's your choice;)

I'd be wary of flying over any "nominated" height at 1 foot above. My height keeping ain't that accurate. I have been known to be as much as ten feet out ;)

There is undoubtedly a safety margin in the nominated heights, but I'd hate to bank on it.

Go for 100 feet above, says I. Or more, if there's room.

Remember a Danger Area and a Restricted Area are quite different beasts.

In the main a Restricted Area is to protect something on the ground from objects in the air. You should ensure that should you have an engine failure you can still remain clear of the restricted area. If you enter it at any time you can be prosecuted.

You are not restricted from entering a Danger Area, but it would be unwise to do so. The operator of a Danger Area is obliged to check that the area is clear before engaging in the dangerous activity. If you enter, you could be prosecuted for endangerment under certain circumstances.

...and (not everyone seems to spot this) remember that some restricted areas are only restricted for Helos (check the notes); usually prisons!

Also remember that you're not allowed in certain danger areas when they're active - they're the ones preceded with a *

FFF
--------------

If you unfold your 1/2 mil chart the (very) small print at the bottom contains a mine of information on Danger Areas etc.

...some of which is very useful during the PPL Nav exam :)

It's a wierd exam - half whiz-wheel, half ruler'n'protractor, half reading the chart'n'Pooleys and half remember/guess the obscure nav fact.... :)