monobloc sink tap fitting

I have a monobloc tap but its footprint is too small for the hole in the sink i,e, it is able to slip into tyhe hole in some positions. I have tried loads of sealant to try to stop it moving around but to no avail, everytime I tighten the locknut up it eventually moves on the sink. There is no large washer under it just an o ring which is the same size as the hole in the sink. I called the supplier, bathstore, and their technical said it is a common problem with these taps so any ideas or is it just try another tap?
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On 28 May 2005 01:36:34 -0700, "frank spencer"

I would guess you need to make the hole smaller, using washers or something.
Rick
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