I can’t say that I’ve heard of an EM conversions of the Hornby Peckett.
In P4, the route has been to use the replacement chassis designed by a friend of mine in the BS4 Scalefour group. It does include EM spacers, although whether any have been built to that standard I don’t know.
The thread about the kit is here: EM/P4 Peckett on Scalefour Society Forum.
There is also a topic about it on RMWeb. There might be some EM discussion there.