ebay mike
Retired, but still hoarding. (GOF)

Not the best quality tool from Poundland BUT it does have hex bits that fit both Aristo & USA trains track screws and Hillman rail clamps. I daresay the bits will not take a lot of abuse but I've tried them out today and they appear to be robust enough to nip up the screws sufficient for my purposes.
One advantage is that the hex bits can be used with a very small ring spanner to enable tightening of screws in confined spaces (I always have trouble on points).

One advantage is that the hex bits can be used with a very small ring spanner to enable tightening of screws in confined spaces (I always have trouble on points).