All RNAV procedures other than B-RNAV ones have been withdrawn as a result of an ATSIN (ATS Information Notice) issued by ATS Standards Department at SRG, CAA.
The P-RNAV procedures that this effects include the P-RNAV SIDs at Luton and the P-RNAV trials in Scottish and Manchester. The P-RNAV procedures are designed in accordance with the Eurocontrol Guidance material and comply with the assumptions of JAA's Temporary Guidance Leaflet 10.
It is unclear as to why the procedures were withdrawn. However, recent indications suggest that work is underway within certain parts of the CAA to get the trials re-instated as soon as possible. Rumour also suggests that a P-RNAV trial could be introduced for Heathrow arrivals in the not too distant future.