DO CHECK with any supplier of planings whether they have an Environmental Permit for Waste Recovery involving the re-use of road planings. Otherwise, the free annual Waste Exemption you could apply for from the Environment Agency to use stuff like road planings at a specific location to create/reinforce a trackway is the U1 Exemption.
Folk can be fined for not being registered for re-use/recovery of Waste if they are reported to the EA.
(Using planings for trackways is Waste Recovery as opposed to Waste Disposal - you obviously have a legitimate need so your use would be Waste Recovery.)
As far as I know, the EA do not check with the LA Planners whether PP is required for any development such as yours before issuing the exemption. (All done simply on-line.) Just to note that all Permits or Exemptions are available for public scrutiny by searching an EA register on-line. Also, sometimes a local EA officer will come check out the site: she did after I'd received my Exemptions certification - I know because I received a telephone call with a query.
In absence of any other forum advice re road planings, I checked ont' web: the only warning was about using planings from deeper resurfacing operations which could contain tar-based rather than just bitumen-based planings !! (How would a customer be able to tell ? Best to use a reputable company, but still not an absolute guarantee. One can ask the question though !)