Dude,
This question has been discussed many times, and no conclusion ever reached.
My own belief is that, legally, you are allowed to descend as low as you like. The reason I say this because you are exempt from the 1000' rule "as required for take off and landing". So if you argue that descending below 1000' is required for landing, then it is legal.
There are many others, though, who believe that this exemption only applies for a published approach. However, there is nothing in writing which confirms this. What's more, there was a proprosal by the CAA, a few years ago, to explicitly ban unpublished approaches. Although this proposal never came to anything, the fact that it existed in the first place suggests that the author believed that unpublished approaches (which is basically what you are talking about) are legal... otherwise he would have had no need to try to make them illegal.
If you agree with my legal point of view, the next question is the practical issue of how low do you actually go. That's something you can only work out for yourself.
Yes I do have an IR, but no I have not really used it, and frankly find the idea of using it is daunting since the training for the IR was a entirely on pre-planned school routes.
My suggestion is to go and fly some routes IFR. Take foggles and a safety pilot if it's a Cavok day. If it's not Cavok, and you're happy you can get into your home airfield safely (given what we've just been discussing) then leave the foggles off, because you want to start learning what real weather looks like. It's very rare you'll fly a whole route in solid IMC, for example, although this is all the IR has trained you for.
FFF
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