i've never heard of buying a bike just because of the tyre size, but i have heard of buying a bike and changing the tyres.
i fail to see why nobody has suggested getting a pair of slick tyres for your existing bike. at around £10 per tyre, it's the far cheaper option.
I'm using Michelin city tyres on my hybrid/commuter bike. i did buy 700x35c but switched to 700x40c to give a little more comfort and shock absorption. the 35c pair went on my sisters bike.... (35c on left, 40c on the right)
even with the massive 700x40c tyres there is plenty of room on my hybrid frame....
and guess what, these are available in MTB sizes and all for only £10 each.
http://www.chainreactioncycles.com/Models.aspx?ModelID=26232
if these are not to your taste then take a look through the road tyre section, find a tyre you like and click on it to see the sizes available. many are available in MTB sizes and are far cheaper than buying a whole new bike.....
http://www.chainreactioncycles.com/...9&CurrentPageIndex=0&SortExpression=PRICE_ASC