There are many Cobra manufacturers with wheelbases over the standard 90 inches. Here is a thread with a zipped Excel file listing all manufacturers. It also lists the wheelbases available.
I'm 6'6" and weigh 275 and I do fit in my std wheelbase SPF. I did a few mods to make it roomier for me. Would I be more comfortable in a stretched 96" WB .... absolutely ... if you like the looks of a stretched Cobra.
Good luck. Can you make it to London show? You can sit in many cars there.
List of Manufacturers