Is HDTV worth buying for me? And what screen size?

Is IT?
I cant get HD broadcast or whatever yet.
If I buy an HDTV I might buy a HD camcorder.
I get digital TV broadcast. (I don't know what to call it).
I watch standard def movies on DVD.

My TV lounge is a complex one to explain. I need someone to recommend a screen size.
The whole lounge is 16 feet by 11ft.
The TV is one one side across the width. On the opposite side on the right side is a door facing the length so it is across the length.

Let me draw a rough diagram. The nos. represent feet. The # represent the door at the bottom and the TV 'area' on the top. That's where all the players etc will go. The hyphens are a 'walkway' where I will not sit and people walk across the house. The white space is where I will sit and stuff on the edge of it.

1-2-3-4-5-6-7-8-9-10-11
2---- #################
3---- #################
4----
5----
6----
7----
8----
9----
10---
11---
12---
13--------------------#
14--------------------#
15--------------------#
16--------------------#

Please recommend the TV sizes that I should get for Plasma and LCD.

I have a choice of two lighting options:
A lamp with a 60Watt bulb at the top right corner of the room where the TV 'area' is. It doesn't let the lunge be called dim or dark.
Another option is 5 bulbs at 100Watts each all across the room in the ceiling. This bright light for me and wouldn't like to have it on whenever the TV is on because of electricity bills.