The answer I am afraid is that it is not possible to find this out.
Wills do not have any kind of registration system. If they did it would stop a lot of people having their estates wound up without a Will where there is a Will but no one can find it!
Sorry I am not in the UK so I do not do the phone call service.
The last Will is the one that is valid and will cancel out the first Will unless the first Will was a "joint Will" where both parties made identical Wills to benefit each other in the same terms at the same time.
These are called mirror Wills and not easily superceded