Claude Butler/Falcon etc are all owned by Madison Cycles. They are Taiwanese frames from the same factory.

Beware with low-end bikes that Hi ten is the lowest grade of steel. Hi Ten tubes are thicker and heavier than a quality steel (eg Chromoly) or Aluminium. Butted tubes may be beyond your budget, but are even lighter, and stronger. One thing to avoid at all costs is cheap bikes with over-sized fat steel tubes. These weigh a ton, handle like dogs, and are just made to look cool.
Also low-end frames often save money by skimping on the alignment process. Both wheels should face in the same direction and be vertical in the frame. On my girfriends cheapo bike, the wheels are so out of alignment, you can see.

The good news with low-end bikes is that the components are better than bike-snobs would like to admit. Not as light as more expensive components, but quite up to the task.

I'll have a look around the manufacturers (Dawes/Raleigh) etc for any good bargains, but the most outstanding low-end bikes I have ever seen are made by Flanders, and stocked by Ken Apps of Hastings. About £200 for an MTB with butted Al frame, chromoly forks, decent wheels and fully threaded frame. Wayne Clarke, the bike shop owner is also a professional wheel-builder and will tune the spokes. This is really important in turning an OK wheel into a truely good wheel.