Keep the account!
I hope they had the wit to retain @UKParliament - simply to stop anyone else using it.
Having never used TikTok, I really don't know whether you can retain dormant accounts. Comment is based on supposition that you can. Have no intention of going off to find out.
Find it difficult to understand why anyone thought it a good idea. I mean, Hansard is a stodgy thing to read. But they never thought to make thinks accessible to UK Youth by adding an "In Parliament Today" section to the Beano, or Judy... So why, just because it is "social media", go to TikTok?