FJ - go for it!
By that I mean, a polite but firm call to the MD, with the threat of Trading Standards, and/or the police.
As you describe it, they've probably committed fraud: they didn't address the problem they were asked to, but supplied unnecessary goods at a high price (am assuming that she already has a sat dish, or was that included too?). If she still doesn't have a dish, of course no 'freesat' box can work, so that would definitely be criminal.
You will need any paperwork supplied, too, and to be absolutely certain of the story before proceeding. They might want to rectify the 'mistake', which is reasonable I suppose, but obviously that would involve putting matters right and refunding the money.
. . .
Was there a problem with her aerial installation? We have had a very wet winter so far, so it's possible water's got into the downlead (they have what's known as an 'air dielectric', which is air spaces in the middle of the cable around the central solid wire, and these can fill with water). It should have a downward-hanging loop on the outside wall, immediately before the point where it comes into the property. This is to prevent water running down the cable into the building, or worse, into the equipment itself. You might prick the underside of this with a pin (go in halfway) to see if anything drips out, but it's not a definitive all-clear if there's nothing. If the cable can drain somehow, it will appear to be OK after periods of dry weather, but go bad after a lot of rain.
If the cable is waterlogged, the only solution is to replace it and often the aerial too (it usually gets in at the top from the aerial's junction box).
Other common winter weather issues include water in the connection box up on the aerial itself, high winds causing the aerial to be blown off alignment (most common if she's on a repeater rather than a main transmitter, as their vertical polarization mean the aerials present more wind resistance), chimney lashings coming loose/undone allowing the aerial to sag downwards, and bits simply blowing off. The other common culprits are the sockets fitted indoors, and the connecting cable between the wall socket and the TV - I've rarely seen co-ax plugs (Belling-Lee) that are properly made off by aerial contractors, and in fact it's quite hard to do well as they're not great connectors to start with). Whatever is wrong, It's almost always something electro-mechanical.
Digits ("Freeview" ones) are deceptive: on a fine day everything will be fine, in poor conditions nothing will be viewable. There are stages in between, but generally it's all or nothing for any given channel. But the channels that "suddenly disappear" depend a lot on the individual transmitter and aerial set up at the house:
The digital switchover has left a number of places with rather sub-optimal channel assignments, making it hard to make (let alone purchase!) a suitable aerial to cover all the MUXes. This is a good place to start for transmitter information:
http://tx.mb21.co.uk/info/index.shtml . Note that the word 'channel' means two confusing things in this context - the TV channel (e.g. BBC-1), and the allocated frequency at the transmitter, which nowadays carries one or more multiplexes ("MUXes"), each in turn carrying several TV and radio channels, and even other stuff like data pages, etc.
The high RF channel numbers will almost always fail first (higher frequencies get lost more easily because of water in the cables and the other possible faults), but there's little apparent logic to the MUX-to-channel assignments. In the old days it was one radio frequency channel per TV channel, but that's no longer the case.
So find out which transmitter her aerial is looking at, look up which TV channels are on which RF channels, and ask which ones are disappearing. The aerial installers should have asked some basic questions and done some simple tests to establish what the problem was.
Hope the above is useful.
E.
PS: In analogue TV days, the most suitable aerial to have was a Yagi design (traditional UHF TV aerial). They are difficult to make to allow for modern channel assignments and for other technical reasons. The good installers will offer Log Periodic aerials as alternatives (they look a bit like xylophones, with a long triangular arrangement). These are usually a better choice for all but odd, marginal coverage areas. That said, about 95% of homes did _not_ need to change their aerials at all after the digital switchover (unless they were faulty in the first place). It's been a nice money-spinner for a bunch of unscrupulous people for quite a few years now, but the 'opportunity' is tailing off now. For another trustworthy reference site (and a good laugh), try Bill's:
http://www.wrightsaerials.tv/ .
