If I recall the plan at Rownhams it's not a simple installation and requires quite of a lot of groundworks to enable it.My understanding is that power is all solved at Winchester so it’s just waiting for switch on.
Rownhams is the first Roadchef project and so they may be getting their ducks in a row before getting started. It is still listed as a “Q4 2021” project so hopefully just a little slow getting underway.