UK PlanIt is a national aggregator for current and historical planning information.
You can use it to search for applications and navigate around all the relevant regions and planning authorities.
Currently 424 planning authorities out of a possible 425 are available. There are details on 19346669 applications and of these 91% can be located on a map.
You can select from this list of authorities with planning data:
Or you can explore using the new Planitogram