I reckon you're reasonably well covered with the lenses that you already have unless you have some specifics in mind. There are puffins to be photographed across at the Farne Islands now ( colin and Randy just been ) so maybe a 300mm prime? I'd certainly recommend a visit to the Lake District in Cumbria. Be sure to get up in the mountains for the best shots and pack some decent walking attire. Not sure what you have in mind but the 18-200 should serve you well. If you're my way on (Yorkshire) give me a nudge. We can have a day out, have a beer.
Unless there is something specific that you feel you can't capture with the lenses you have already, I would just take the 18-200 and the 35. And with the money that you save by not renting, maybe pick up a 50/1.8 for low light?
I really don't like the 18-200 or any other super ratio do anything ok but nothing well type lenses, so I'd not bring that, but that's just me.
The 35 f/2 is an underrated lens for scenics though and in my opinion. using the old cliche of "f/8 and be there" this lens really performs beautifully to me. At f/5.6 and f/8 it is razor sharp and without any visible or field relevant distortion. Some claim it lacks a bit of contrast, but at those f/stops mine is just about perfect. I can add a little if I need it. You'll need a tripod or monopod shooting at f/8 with a polarizing filter, but I do anyway. My carbon fiber travel tripod is four section and only weighs around 2 lbs.
I think it's a super keeper. I'd carry that 35 f/2 along with an 85 f/1.8 and be mostly happy all over my vacation, but I shoot mostly full frame so my opinion may not be of use. You might need something wider.
Another travel combo for me is the 35 f/2 and a 70-300 f/4.5-5.6 VR. I use a little belt pouch to carry one or the other. A 12-24 and that longer zoom might also be a good combo.