If you take a look at the older machines such as Wadkins, Cooklsey and Diminion you will notice that they are built of substantial cast iron with tables that don't lift up. The reason I believe is that it provides the ridgid structure necessary to maintain the two planer tables in alignment with each other when setup. If you think about how you establish if a hand plane is tuned up, one of the checks is the flatness of the sole. A few thou out and the hand plane won't perform as desired. The same is true for how accurately set the two tables have to be to each other and to the axis of the spindle. With very few exceptions, modern light weight machines don't have the rigidity or lifting mechanisms to repeatable return the tables to the exact position after they have been lifted up to convert the machine to a thicknesser.
I would recommend either a Sedgwick (which are still built and are made in Leeds) a Wadkin, Dominion or Cooksley. They are all built to last generations and will provide superb service. If possible try to avoid adding wheels, machines and castings do move as they are moved around a floor. It's not much, but can make a difference.
A Hammer or Felder machine would also be a superb investment, however they are likely to be outside your budget. These are the modern lift up table machines that can I understand achieve the level of accuracy required and hence a price to reflect the engineering involved.
For ease of setup try and get a machine with a Tersa or similar block. Secondhand machines with these fitted are rare and command good prices, but with your budget you may be lucky. A Tersa block or a Spiral block can be fitted to upgrade a machine at a later date. They are however horribly expensive to buy separately to do an upgrade.
