Getting there by train is the easiest option. Either from London or Birmingham. Parking is expensive, and the long stay car park is a very long way from the terminal.
Check in is like anywhere else. The centre security doors flow quicker that then end ones. If you are of limited mobility I would expect that assistance would be provided.
You will need to wait in the lounge until the flight gate is announced. When the gate appears on the screens, you will need to catch the little train out to the gate - allow ten minites for this. Then you will need to go up in the lift from the train to the gate. I have no idea how to get from the gate (on the second floor) back down to the ground (to board the aircraft steps) any other way than the stairs, but it must exist.
Coming back, you will only need to go up to the first floor, before back down to the train back to the terminal. Passport control is usually packed, so allow twenty minutes.
There are plenty of places to get food and drink, including small outlets in the gate area (so you can get stuff after the train). As you are flying to the EU, they will hold your duty free to pick up on the way back.
Simon.