Need some advice please

Well done on wanting to change things!

I'd second the advice of going to a decent bike shop. At your height and weight they shouldn't be trying to sell you a lightweight racing bike.

I'd say a decent hybrid with a wide range of gears, 36 spoke wheels and 35mm tyres or fatter. Go for slick tyres if all your riding is on paved surfaces; knobbly tyres on the road can be really tiring.

And if weight reduction is one of your aims, my experience is that it's far easier to do it by eating less than by exercising more, but both is better still.

I failed miserably / repeatedly with trying to eat a calorie controlled diet 24/7; I just don't have the willpower and if food's there, I eat it.
But I do seem to be able to do the 5:2 diet. Maybe because on a fasting day I know I can eat normally the next day. It's all mind games, but it's the only way I've ever found of outwitting my inner glutton.

As above, I think a decent ish hybrid would be ideal as a starter, you could do a lot worse than the Voodoo Marasa from Halfords.

Expect to pay at least £300 for a bike that is worth buying (good enough to not put you off and well built enough to not require excessive maintenance just to keep it working).

The Marasa
http://www.halfords.com/cycling/bikes/h ... ybrid-bike

Again another thumbs up from me - Cycling is fantastic and once your hooked you will be hooked for life !

At this stage I would not worry too much about specific equipment, Getting the fit correct is the most important, As you progress your requirements may change so I don't think a specific model of bike is what you need. As a general rule a hybrid is good start but again fit is everything so maybe consider getting a proper bike fit done. The decent bike shops will do this for you either for a small charge or if you get the bike from them they will usually do this for free. Getting your position right is the key to comfort.

After the fit then look at something that has a good set of wheels (32 spokes are ideal) and wider rubber for added comfort.

I echo others in that avoid any bike sold by a supermarket or places like Argos - They WILL be cack! Try your local bike shop or consider one of the bigger outlets like Decathlon - Their Btwin range is very good and great value for money.

Also just remember as well there is no such thing as bad weather only bad clothing so initially consider getting something that is quick drying and comfy along with a breathable waterproof jacket - Thin layers are better than 1 thick layer.

Once you start cycling you will look in pity at all those people stuck in bus/train/car.

How I started:

118kg, 182cm
Hybrid bike (Giant Boulder ALU Lite) on Semi Slick tyres Hutchinson something or other.
I traded some PC Parts for the bike with a former work colleague.
A short, flat and mostly off road route of about 6.6miles in maybe 45minutes.
I rode 2-3 times a week and avoided riding in bad weather.
I smoked back then too.

Over time I moved more and more of the commute to roads as I gained confidence in traffic and to speed up (or really to reduce the ammount I needed to slow down) I also moved to road tyres (Gatorskins, Sport Contact and Durano), upgraded parts on the bike as they failed using YouTube, BikeRadar and similar sites for advice and videos. In doing this I gradually added to my tool collection and have distilled what to carry when commuting down to a pump, a tube, two tyre levers, some patches (leeches/scabs) or a tubeless repair kit, a chain tool, a multitool, some plasters, some cable ties, spare batteries, some electrical tape. I figured out how to adjust things on the bike for a better fit for either speed or comfort I also stopped smoking as it was slowing me down, if you can't beat addiction replace it. Same with food, I made sure I was always stocked up with fruit, soup or home made flapjacks and protein powder instead of eating the high carb, high fat that the local cafe served.

I sold my car to remove the temptation to drive on rainy days and committed to riding through two of the worst winters we've had in my lifetime. Most days when weather is extreme, snow, floods etc... I'm the least affected as I'm not trapped by traffic or failed busses/trams/trains.

After I was used to the commute I started doing longer rides outside of the commute and began doing a lunch ride and adding hills to the commute. I got the minimum commute down to 22 minutes (with good luck at the lights). Then I got a road bike and started doing Sportives and other events, my first was a 104mile ride. I think I got down to 80kg that year.

Now I'm not a racing snake, but I can go out with a cycling club on my road bike (carbon fork, tubless tyres, hydraulic brakes) and do 100km without a second thought. This year I rode Coast to Coast in a day (150 miles) and am looking to do a 300mile 24hour ride next year and have signed up for the Dirty Reiver (200km of dirt road in Keilder, Northumberland).