This is the first time i've looked at a diet as a lifestyle change, and am looking to eat really healthily getting the right amount of nutrients etc and trying to make it almost a hobby rather than a challenge.

I have never really known much about healthy eating, but things i have gathered and plan to follow :

my meal should be 1/4 protein, 1/4 carbs and 1/2 veggies
to eat 2-3 handfuls of nuts a day
drink plenty of water obviously
eat my 5 a day - i'm planning to make smoothies and soups so this should be quite easy!

i'm also going to drink a cup of green tea every day - put as i'm not a huge fan of it - would it be ok to put a teaspoon of honey in it?

What are other essentials for eating healthily?

I would just say I don't know about 2-3 handfuls of nuts a day. I love having (and do have) nuts every day, but if a handful is 1/4c, then 3/4c of nuts (say, walnut halves) is 490 calories. I usually have about 1/4c a day or less.

I personally wouldn't worry about a tsp of honey a day, if you're not teaspooning that honey all day on lots of things. If you don't have sugar every day (except in one cup of tea) you may find you need less and less. I'm presently using agave syrup instead of honey (because it dissolves so nicely), and I use about 1/4 or maybe 1/3 tsp (eyeballing) for a cup of coffee.

Ah i just read somewhere about 2-3 hadfuls. How many brazil nuts for example would you say was in a handful?

Check out FitDay.com and you can look these things up.

Brazil nuts, 1c shelled (32 kernels), 918 calories. 1 oz is 186 calories. 1 oz is often used as a "serving" size, and when dieting, 1/2 oz may be more appropriate for some. By the above numbers, 1 oz is about 1/5c, so say ~1.5T (which is a lot less than 1/4c = 4T)

You'll have to take a handful, then use a measuring cup to tell you how much a "handful" is for you. Measuring by handfuls can be tricky. The amount you take tends to creep up and up. Measuring with a measuring cup at first is probably a good idea. I'm not measuring constantly and not calorie counting anymore, but I needed to for a while to learn a new "normal." And even then it's not for everyone. Many will always measure and count. But not all of us