P0128 2 weeks after replacing temp sensor

[JonathanLondon]

Local stealerships are a p.i.t.f.a...

Many thanks for your continuing advice.  The garage report that the thermostat is not closing properly and as a result the engine isn't getting up to temperature and hence the P0128 error triggers after 23 minutes.  They were suspicious about how long it was taking when they replaced the temperature sensor (at my request), a couple of weeks ago.

They have asked Vauxhall to quote for the thermostat, and await Vauxhall's return call.  Locally Vauxhall parts are on a seven working day lead time, and that's once they get around to calling you back.