hi mate 1st things 1st not sure if u already know but ull need to contact council, building and construction and give them 48hour notice without this u wont be able to carry out ur work. they will charge u a fee of about £110 which u will have to pay. and fill out a appliction form.
Now im not sure if u planning to do it urself but i removed my chimney a month ago my self never did 1 b4.
my chimney was like u have in ur plan there.
now it is best to get some1 in to look at it for u like cram mentioned b4. but just to run through afew things with u that u wil need to do or the building and construction chap will not pass it. and believe me they do come out and look at it especially if ur not a builder
they came out 3 times to look at my job
1. u will have to contact council, building and construction
2. once u have taken out chimney u will need to put a Steel Girder in place this is 1 if ur not sure what it is
http://thumbs.dreamstime.com/thumb_6...47057Lr2Oz.jpg mine cost £100 i used a 13ft by 8 inch.
thats if ur not going to take the above chimney out so that it can support all the weight above
P.S the Steel Girders are very heavy so u will need 2 to 3 people to lift and put it into place.
3. u will need to get a steel plate made and bolted onto the wall were the chimney volt is. mine cost £25 in total.
4. u will need to use the fire proof plaster boards (Red Plaster Boards) around the Steel Girder to protect it. about £6 a board most ull need is 2.
5. u will need 2 x reinforced concrete blocks which have steel rods in em these will go under were the steel girder will sit on both sides of the wall. cost around £15
A few Tips when taking out the chimney DO NOT USE A SLEDGE HAMMER the reason is u may damage ur neighbours wall. best thing to use is a Club Hammer like this
Forge Steel Fibreglass Handle Club Hammer 4lb - Screwfix.com, Where the Trade Buys a
and a wide chisel some thing like this
Sumo 2¾" x 8½" Masonry Bolster with Guard - Screwfix.com, Where the Trade Buys
U will most likey come across bricks that are half sticking out of the wall and the other half in the main wall all u need to do is chisel it off, always chisel so that the impact is down and not into the wall . also remember that some walls in the old buildings are just single walls so if u for example took out a full brick u would be looking into ur neighbours house lolol

but most i do know are doulble walls so u have a wall on ur side and ur neighbours will have one on theres hope that makes sense
For me im really glad i removed my chimney it was well worth it although its very very messy just remember to close off ur door when u start i used duct tape around th door.
I hope some of this info helps u in some way or the other and if u need any other info ill be glad to help