One of the few projects that have become cheaper with time, Kenny.
These days I would be tempted to go for a flexible panel(s) stuck straight onto the roof. Less wind resistance and easier to clean. Getting at the crud under a big panel is not easy when atop a ladder. Plus they collect fewer twigs when passing under trees and close to hedges.
Do not forget to use UV grade cabling on the roof and for maximum efficiency, use an MPPT type charge controller that will provide a feed for the engine battery. I had one (Can’t remember make.) that supported a remote control panel to show battery voltage, capacity and charge rate.
NB I found British sourced panels and accessories very expensive. I bought a kit from Top Accessoires in France and fitted it myself. I cannot seem to access old messages on this list, but I posted details back in about 2004 or 2005.