We have recently moved in to a flat with a newly fitted bathroom. Despite this the mixer tap on the sink (see attached pics) has started to leak - water dripping from the fixing bolts under the sink. Attachment to water supply is completely dry so that's not the problem. Removing the tap, I can see water building up above the mixer unit (see pic). This seems to be the source of the problem: if I dry this, it fills up again. Presumably this then drains down slowly through the whole unit. So, I guess either the whole thing is faulty and needs to be replaced (60-120 quid, depending on what I replace it with), or there's some rubber sealing washer that needs replacing or is not seated properly. So far, I haven't managed to undo the large bolt that seems to be the only way into the tap to investigate further.
The question I have is - is it worth trying to open the thing up further? If so, what's the best tool to do this with? Or, should I just given in and buy a new tap?
Pic 1: The tap, intact.
Pic2: with the top removed. You can see water building up in the top.