How about looking at a chart see if there are any natural or manmade transits you could use or back transits .
If you dont have a set of charts for the solent then buy the Imray C15 as covers all the Solent or you could download from
UK Wide Harbour Pilotage, View Full Size Marine Charts Online
only a small joining fee and you can zoom in and out to look at the detail.
also you can georeference them so great for passage planning .
Tim