i was in the same boat couple of months back and couldnt decide between tt 300 or the navman 510, both are good but in the end i went for the navman after seeing the size of the tomtom and with the dash mount makes it a monster IMO,navman fits nicely into my pocket well pleased with it
Pretty sure the one for sale on the link above (the classic) wont let you search by postcode which is a must ..could be wrong on that though