Hiya and welcome! I was very much in the same boat as you when I started, only a bit younger. I've lost 4.5 stone in under a year, and although I've put a bit back on, it doesn't stress me out. If you follow the plan (start with Extra Easy) you should have phenomenal success from the start 
You've done the hardest part which is turning up for the first meeting and facing your weight. I found that very embarrassing but now I look forward to going every week! Us men are in a minority both on here and in group but there are some amazing success stories. We're lucky in that we tend to be very focused and also have a much higher metabolism. So by sticking to plan the weight will fly off.
When I joined this forum I wrote a few tips for someone based on what worked for me in the beginning, so hopefully these will help:
1) Read all the books cover to cover. It's well worth spending a whole day really getting to grips with it.
2) If you see any of your fave foods in the free food section, jot them down.
3) Keep your "food diary" religiously, at least for the first few months. The "lifeline online" website and mobile site (not the app, that's useless) are pretty good for this. Also keep the journal part - what meals you had that day. In future if/when you have a bad week you can go back and see what you did. This will be a Godsend.
4) Weigh-in EVERY week, even if you don't feel like it, and ALWAYS stay to group. You'll get to know people quickly, and their encouragement will really pump you up. Later on new members will find your own experience and support invaluable.
5) Make sure your family and friends know you're serious about this and ask for their support (for example not to waft cakes under your nose when you visit!)
6) Stick to the plan 100%, that's the only thing you really have to do. Do that and the weight will practically fall off, guaranteed!
A few more:
7) If you like takeaways, just adapt the recipes and make your own with free food. I'm not one of the SW-ers who obsesses over Mullerlights and Mug Shots, I do my own thing, albeit mainly to save money.
8)
Have all of your syns. With your starting weight (similar to mine) you will lose quickly if you go the full 15 each day, and you won't get cravings or feelings of abstension that you are going to encounter if you don't already. On SW, NOTHING is banned! Eat whatever you like within the plan! If you like lager, have lager. This won't work for everyone but I forced myself to get a taste for Tesco Value lager at 3 syns per can (and dead cheap). Ice-cold with a slice of lime on a hot day and it's not half bad.
9) Try the "Body Magic challenges" on the website. I rediscovered a love of walking, but you can use them for cycling too and they are a great motivator.
10) Don't set a final target based on your BMI, it is flawed for people of our height.
11) Never stress out about food or weight loss, and definitely not about the odd gain which sometimes happens.
Good luck and let us know how you get on!
