There's a lot of info on honestjohn's website about landrover's with dpf problems and oil dilution.
My 2005 Focus did not have a DPF.
This
Good Luck with the not fit for purpose route. You will find the information regarding the DPF is in the hand book. Anyone who buys a diesel must be aware of issues with DPFs, if not, you did zero research.
As for the oil diluting, this is similar to what happens in PSA engines. A small amount of fuel is added to the oil for regeneration, however, if the regen does not complete, it will try again under the right conditions, and will add a small amount of fuel again to the oil. My DPF regened ever 500 miles or so, depending on how much motorway miles I drove.
It sounds like every time you hit the magical figures for a regen, it is not completing, and thus diluting with fuel. The simple solution is to go for a blast down the motorway for 20 minutes. The option to defer is an OK idea, but like yourself, how many times would you defer it? Many times, and then the DPF gets blocked and you moan to Land Rover.
Some cars can have a forced regen (PSA allow this option) when stationary through the ODB 2 port, but do not attempt this on a hot day.
If you are only doing 7.5k miles a year, you do not really need a diesel
The twenty minute run is simplest - you would spend more time and money sorting it any other way.
Doesn't even need to be 70mph, 60 would do it.