In reply to 2E0XTL:
It depends on what you want to do really if its all SOTA, a handheld FM would get you some contacts but is limited longer term. It might be a good idea before you do anything to speak to someone near you who is into microwaves now, this could help. Also you will get an idea of activity in your area and maybe some help and advice. The “UK microwave group” is a source of information at £6 per year subscription if you get really into it!
I was lucky and picked up a DB6NT transverter secondhand which allows me to use all mode from my 817 but these are pricey new(about 1W output) I operate contests as well from hilltops for fun and there is a core of good operators on there on ssb/cw.
On antennas I have no experience of verticals, I use horizontal beams which are easy to use on the hill because of the tiny elements, they have much higher gain for a given boom length but are very much more directional! You can make a short quite high gain yagi, there are lots of designs about on the web. For example (but loads of others:
Hope you manage to get on there, its abit more specialist with fewer ops up there but an interesting challenge if you want to look beyond FM.
Hope some of this babble helps.