I've looked at the AWARE £149 moving map and it looks very good.
However, I looked at the 1:250000 chart updates, which add another £120, if you want the whole country.
Then the updates for the aforementioned charts which are "yearly subscription charges are £25 per paper chart". Of course there are eight charts for the U.K.
It all adds up.
If you include their navigation upgrade, well you might as well go for the £500 -600 alternatives.