...some will spend £10,000,000.
OK, well it may be helpful if you post how much your company spends on it (if you don't mind divulging this information).
I can't think of one company speading that amount on advertising PCM.
I can't think of one company speading that amount on advertising PCM.
The old rule of thumb was 10%. However, things have changed thanks to the Internet and I have no idea these days what the average % is.