I have been in Sevenoakes Glasgow a number of times, parking my car in adjacent side streets each time. Never had a problem, I must have been lucky. Or maybe it was the fact that my humble BMW 3 was parked alongside much more esoteric machinery owned by locals. Why not do as I usually do where I cannot park adjacent to the store. Before buying I tell the sales person that I will bring my car to the door and he/she should hold the item and be ready to help me load it when I arrive, never had a refusal yet.
The staff in that store are certainly of the variety that does not even look in your direction unless you ask for service. Some people like this approach, others do not. However, once asked I found them helpful but lacking in knowledge of some of the kit they sell. I had the opposite experience of Alan James Hi-Fi to that of the other contributor. The owner told me that my "body language" convinced him that I was not going to buy anything that day ( true, but it still annoyed me). What was worse was that after leaving my phone number and asking that they ring me when they had available some speakers I was interested in, they never did call.
After looking in most of the dealers in central Glasgow I found that Stereo-Stereo (in St. Vincent St.) were the best for me. Very helpful and very knowledgeable about the kit they sell.
Unfortunately I think they don't stock any of the subs you are interested in. They do B&W and Anthony Gallo. I bought a Gallo sub on their recommendation and have not regretted it. Great sounding little sub and very neat in appearance so I got it past the wife no bother.