Monroes is a decent shout , as 'bluereddish' says ...... it gets mixed reviews , but gets far more good ones than bad ones , and you really can't get any closer to Piccadilly Station than this ..... only problem can be possible bus and tram noise outside ...... there aren't many rooms , so book as early as possible ..... and if rooms really do cost around the £25 quid mark you'll be hard pushed to find anywhere else cheaper in the city centre.
Another cheap hotel option is Merchants hotel , back piccadilly (link below) ..... seems to have basic rooms for about £35 for the night in question .... not sure whether that includes breakfast or not not , you'd have to check ..... it's approx. 5 minutes walk to the station from here.
<a class="postlink" href="http://www.manchester2002-uk.com/hotels/manchester-hotels/merchants-hotel.html" onclick="window.open(this.href);return false;">http://www.manchester2002-uk.com/hotels ... hotel.html</a>
On a slightly dearer note you could also try the Gardens hotel in Piccadilly itself ......... or you could ask the Waldorf Hotel if they do overnight stays!