Forgive me, because I'm going to be using standard units instead of stones.
Okay, so you want to put on muscle mass. First off, no matter what, you want to put the weight on slowly and gradually. Average and healthy amount of weight to put on is about 5 to 10 pounds in a month. If this sounds wrong, anyone, please feel free to correct me. Also, when you're putting on weight, that's just what you're doing: putting on weight, which is going to be comprised of both lean muscle mass AND fat. It's unavoidable; the human body works that way. You have to accept that. On a side note, I told a buddy of mine that same thing, and he then decided against putting on weight because he "didn't want to get fat." There is a way to minimize the amount of body fat you put on, but we'll save that topic for later.....and for other people that have more experience in that than me.
Anyways, primarily, you're going to want to figure out what you daily caloric need is by finding your resting heart rate and figure out your body's resting metabolic rate. Once you figure out how much calories your body needs in a day, you just consume more than that. Yeah, it's simple. You gain weight by eating more calories than you need. Now, you don't want to start eating 5000 calories worth of food a day right away, or ever for that matter. You have to ease into it. Start by upping your calories by 100-200 over a week or two. When you get used to that, increase again by 100-200 again, until you reach your calculated caloric need.
When you're eating, most people find it's easier to break down your food needs into smaller meals that are eaten frequently throughout the day, about every 2 to 3 hours, totaling to about 6 to 7 meals a day. You want to get most of your caloric needs from foods. Protein shakes are a good source of extra protein and calories but they are supplements
and should be used to supplement
your caloric needs, not be the base.
Now you mention you're a fussy eater? Well, you're gonna have to eat some foods you may not like but you need to eat because of their nutritional value or monetary value that will fit your budget, but it should be possible.