JJ'S unfortunately is now gone used to take my old cars there.
The only place i can think of near chester is WGT Auto Developments RX7 specialists in Northwich about 15 miles from Chester City Centre.
They have a Dynapack Chassis Dyno (direct to hubs) not been there myself but was thinking of taking mine there sometime.
My mate lives in the apartments opposite usually loads of RX7'S outside on a Saturday morning so you would probably have to book in advance.
According to their website power runs £50 with colour print out.
www.wgtautodevelopments.co.uk