Grantos

I havn't time to fully go through your css however I did notice you are saying a lot of widths, e.g.
 

.pagewidth,.pagecontainer { width:895px; margin:0 auto; }
 
and
 

#ebaybeheader { width:895px; height:207px; background-image:url(http://www.bathroomexpress.co.uk/images/ebaystore/ebay-header.jpg); background-position:0 15px; background-repeat:no-repeat; }
 
Now if you add your left content and right col widths you get 895px ... the problem is of magic space that IE is so fond of (like the weird 3px space on UL inline menus).
 
I suggest making the left col 710px and leaving a 5px room for error. A lot of your css can go ... remove the width to anything inside the left or right col as it's not needed, its container is already set in width.
 
Also look at the following;
 

.baths-sidebar1 { float : right; width : 180px; padding-bottom : 4px; border-color : #ff0000; border-style : dashed; border-width : 1px; }
 
This (in IE) will make a 182px box due to the extra 1px each side for a border. This is a good clear method;
 

.clear { clear: both; }
and then just use <div class="clear"></div> to clear and make a new row / break alignment.
 
I hope this points in the right direction.
 
One last tip is I was once told is "css is about what's different - you don't need to repeat yourself"