Freerein is expensive unfortunately pibstar - I think it's £435 + first night accomodation and meals, but nice to get out and see different places on the trail. It's not a bring your own, but it is the place to place one if that makes sense - I've gone for one with a guide, but you can also go it alone if there are 2 or 3 of you. I'm not _quite_ that confident yet.
If you are worried about your standard loopyh take a look at the freerein onto the trail - my friends did it with a few weeks and about 6 months experience and both enjoyed themselves hugely. They have some unbelievably calm horses for the nervous, I rode the most obedient creature I've ever come across there (Friday) - I spent the first few hours waiting for the tantrums I am accustomed to but she was impeccable the whole trek. Back, front, any pace, side by side, awful weather, left behind on her own, the lot, never anything but happy and responsive - to be honest it was almost wierd, I'm not sure what to do with myself without the customary bouncing on the spot at the canters and strop about who gets to go through the gate first!
Cae Iago is also good for nervous - you need to be competent as its a long day and steep hills, but the horses are very safe and well used to the job and lesley and the guides are very reassuring somehow!
Northfields horses are not quite so steady in general and definately quicker, so as it's a very long day with gallops probably best not for a first time nervous rider. I am nervy myself and love it, but I'm also very used to hacking out and speed doesn't bother me at all (it's the horses that always feel like they want to be trotting in walk that do me in - oh and HILLS!)
As for experience, my first time (cae iago) was about 18months into learning to ride, since then(2 years) I've done about 2 weeks a year plus once a month local hacks so I am used to being out and about as much as a non owner ever is I think. On the downside I'm horribly unfit, was never very talented, stopped the lesson after 2 years or so and am a nervous rider to boot so not exactly charging around the place willy nilly. Experienced novice is what I usually categorise myself as
Cantering out on a hack is much easier than in the school though so I would think you'll find it easier than you expect?
aj xx