I was originally going to go the same route you are planning now and after doing plenty of reading on this site i decided to just save up and do it right. You won't regret it. If you are going to run 250 watts of cfl you are better off saving up and getting a 250watt hid light. Your yield will increase dramatically and the bud will overall be better.
Onto your questions
1.as originally said above, you'd be better off getting a 250 hps and getting a better yield, but two will probably work for one or two autos
2.Depends on how well ventilated and filtered the tent is. You will want an exhaust with carbon filter to help give rid of the smell.
3.with that much light you will probably need a bigger fan than a pc fan, and a bigger fan to pull through a carbon filter
4.your timer should come with instructions on how to set it up. usually its flip the pins one way for on time and the other way for off
5.i have a 125 watt cfl i use for vegging, it's currently on an 18/6 light schedule and turns on and off without problems, it's designed to be turned on and off
6.not too sure what the rule is on this one. i think it depends a lot on the quality of the fan you buy
7.not too sure about the uk, but you can choose whatever times you want. some people have the lights on at night to help control the heat. whatever works best for you
8.they can grow up to 90 degrees, but they will grow slow compared to being under 80. i have mine in a room where i have a window unit set to 70 all day for the box to stay cool
9.if done correctly you can get on ounce off of one plant. I dont know if being an auto effects the yield that much or not. It also comes down to a lot of grow experience
10.probably not very effectively by itself, but to help with a carbon filter it should.
https://www.rollitup.org/do-yourself/422039-cheap-smell-masking-device-things.html some thing like that could be easy to build and you can use febreeze instead of pine sol
11.i don't know about that one, i'm in the us so i dont know what stores or sites you have
12.when they need it. a lot of us first timers tend to overwater. most do it based off of the weight of the pot when it's dry versus when its just been watered
13.as in trimming the buds after harvest? all depends on how fast you trim and how clean you want your trim
14.
https://www.rollitup.org/advanced-marijuana-cultivation/369528-low-stress-training-lst-guide.html
15.not sure about this. a more experienced grower will be able to help you here
16.that's probably close to as loud as a standard computer fan
hope this helps.
