It shouldn't matter who your relationship is with. Mine was with the lease company too, I was upfront with the dealer about it and whilst they did ask if I could influence the ordering dealer with the lease company, which I did ask about, I was honest and said I didn't think it was possible.
I spoke to Leicester and Derby dealers ( both Sytner i think) and Lex ordered with Bradford (RRG Group).
Leics will get all the service business though and you never know I may order a private car from them sometime if it the experience is good, which it has been so far!
As an aside I found Lexus dealers the most agnostic about the lease experience. Local BmW, Merc and Audi dealers didnt want to even talk to me once they found out I was a Lex company car user! No chance of a test drive, or even some basic info.
Car will be along soon and then you'll forget about how long a wait it was.