How secret is our secret vote??

[MrsSchrute]

That sounds far more conspiratorial than I intended, but here is my question ...

So when I go in to the polling station to vote I give the Clerk my name, address, and show my photo ID.
The Clerk read out a four digit number next to my name on their list, which the second Clerk writes on a list next to the serial number of the ballot paper I'm given.
I then go into the booth to vote.

So that means that every vote is traceable? Right??

Technically yes, but all the bits are securely stored separately. They can only be reunited with a court order if for example there was an investigation for fraud.
It is extremely unlikely to happen.