You have probably gone into overload with the advice you've gathered, but it you can take a little more from a guy with walking experience in the UK, Australia and NZ...
Work on these base principles....

* The weather in the UK, especially in hill country, is lousy; ie cold, windy and wet. You don't say what time of year you will be hiking, but it doesn't much matter. Prepare for the worst and enjoy the best. If you are walking the Pennines in late Autumn, Winter, you will run into seriously hypothermic conditions.

* The British make extremely good foul weather gear, and general outdoors kit for the above reasons. I would not buy gear that does not have to be 'run in' until I got to the U.K.

* Your feet are your best friends.. pamper them on the trip. Most boots you will buy today are lightweight which is OK as long as they provide good ankle support and sole cushioning. Do not confuse 'walking' boots with 'climbing' boots with fancy Italian names. Do NOT break in new boots on the walk itself. Too late.
* If you are not sure, get your feet examined by a reputable podiatrist. Many of us have varying degrees of flat feet. You may have time to get personalised inserts for your boots. If you do, make sure you buy new boots to fit inserts...
* Walking in Britain is a relatively civilised affair. You are never very far from other people. Get the appropriate Ordnance maps and use a compass.

* You will suffer from an over-burden of gear and gadgets and general junk, unless very careful. Spread out what you would like to take.... and then halve it.. you will be glad you did.

* From your rough plan I would say you are trying for too much distance in too short a time. Not enough time for smelling the roses, taking a day off here and there IF the weather is nice.
* Ease into the walk... no matter how fit, you still need 'time in the saddle'; give your body time to adjust to boots, pack; you can punch the kilometres out later in the trip, if you want to...

Hope this helps.. safe trekking...!!!