Are you sure that they are not suggesting that you would get too strong a signal and require a attenuator?
It seems strange to suggest that 'too much interference' could be a reasonable suggestion...
You are so close to a powerful transmitter that I would have thought that even a very small aerial will get you a good Freeview signal.
The aerials that have a large number of elements are for poor reception areas. Their design makes them more focused and this provides more signal and makes them more directional.
I have never seen a situation where a terrestrialdigital signal in the UK is too strong. For one thing, even at Crystal Palace, where the analogue signals are at 1,000,000 watts, the Freeview ones are at 20,000 watts.
I suspect there may be conditions where you can get co-channel interference effecting the digital channels, but the COFDM transmission system is supposed to deal with this.
I'm always interested to hear what people are being told about Freeview reception.
In their application for a franchise "That's Solent TV" stated that they would provide seperate news bulletins for Southampton and Winchester, the Isle of Wight, and Portsmouth. Does this mean that the seperate bulletins would be broadcast to the whole area covered at separate times or will they be broadcast simultaneously using a "red button" as is the case with the BBC?