Yes, participating locations almost always upgrade me. I'm not really interested in a discounted price as I bill it all to expenses anyway, it just p!sses me off that there are only 5 locations in the UK (plus Marble Arch that I use almost weekly) that actually upgrade me regularly.

As someone who rents a car at least 3/4 days every week of the year, these little things like worthless vouchers irritate me.