I have ordered mine yesterday as a lease from National Vehicle Solutions who have advised a 12 week lead time? they did say its a factory order
Ignoring WLTP type approval, 12 weeks for a factory order is probably realistic. However, according to VW’s website, only the new Touareg and certain models of the up! and T-Roc currently have WLTP type approval. Any Golfs built from now on will be 2019 model year, and need to be WLTP type approved.
So, I’d say 12 week lead time for a factory order (2019 model) looks unlikely if the Golf GTI PP hasn’t yet been WLTP type approved. There may be unsold 2018 model year stock in the UK, but these will be pre-WLTP type approved cars that need to have been registered by now - I think the registration deadline date was 15th August.