Is it possible for UK residents to invest in Vanguard's VGT

The short answer seems to be no:

Unless you’re able to prove you’re a ‘sophisticated investor’ then practically all platforms and brokers will refuse to sell you ETFs based in the US (also known as US-domiciled or US-registered ETFs) because these products do not conform to European UCITS regulation. This piece explains why we can no longer buy US-domiciled ETFs.

While it is possible to open an account with a US broker if you’re resident in the UK, you will still be denied US-listed ETFs (even if you’re a US citizen) because the regulation is deemed to have “extra-judicial reach”. In other words, it’s your address that counts and not the legal jurisdiction of the company that you’re dealing with.

Source: https://www.justetf.com/uk/academy/us-etfs-how-to-buy-the-best-equivalent-etfs-in-the-uk.html