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Have a look at these couple of links where this has been discussed before. In essence the 11+ test in Warwickshire is set by University of Durham CEM, as is the Birmingham 11+. It contains Maths, English, NVR and VR. No practice papers are available. Also it is likely to change every year, so whats good for one year might not be for the next.viewtopic.php?f=37&t=10123viewtopic.php?f=37&t=10721
The answer to this, I believe, is to keep your preparation as wide as possible using as many materials as possible - expect the unexpected.