I appreciate what you say Dave. In fact as far as big companies are concerned I very much doubt that there is any real ROI. If is just a vanity exercise under the excuse of brand awareness and the PR department will fight tooth and nail to protect their budgets & jobs.
There is no doubt a saturation point where brand awareness becomes so prolific that consumers wouldn't dream of buying an own brand cola when put along side Coca Cola. For large corporations is makes perfect sense to drive the message home over and over until their brand reaches the giddy heights of household brand.
For the SME however targeted advertising does work and the latest fad is vehicle livery. LBC London's biggest private radio has for example over 250 taxis running around with their logo and it is quite cheap to do this yourself. I know that I am about to try it.
Best of luck with your marketing. I think for real World businesses or Web businesses with a strong regional service delivery, targeted regionalised marketing can work to great effect, I just can't see the same happening for an Internet-only business who's target audience is UK or even Worldwide.
For Web businesses it tends to happen the other way round, they become an Internet household brand, eBay, Google, Amazon, Asos and so on and even then they use very limited and very targeted real World marketing.
EBay are a great example, they hit the TV screens only during peak shopping months usually either side of Christmas. You will not see them on TV or in the papers throughout the year.
We only need to look back 7 / 8 years to see what happens to Web businesses that throw millions at real World brand awareness in huge publicity drives, only for them to be forgot and go bust months later. This was a mistake repeated over and over just before and during the dotcom bubble bursting, the business owners failed to understand that their core markets could only really be reached through the medium they operated through, the Internet.