Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
What TV to buy is of course ultimately up to you. I am assuming you want one that is at least the size of the former TV, but not too large for the alcove either.
What Freeview TV box you have is kind of an issue... there are Apple, Roku, Panasonic, 'Now', and Manhattan brand boxes, among others. Assuming you have a typical one, like the Manhattan brand, that means you need an HDMI connection port on the TV for the Manhattan box to hook up to.
What kind of screen to buy is again up to you; But for various viewing subjects, various types are appropriate. LED TV is generally speaking good for most viewing. For really still content most of the time, a plasma TV might produce slightly better detail - but it depends highly upon the exact specifications of the particular TV.
Here's some that are about the size you are looking for and probably good-enough or better:
is a 43 inch LED TV, with the two HDMI ports you need for both the Freeview box and the DVD player / VHS player connection, plus other features. It is $ 947 (possibly $5 less from a discount the web page may offer, perhaps.)
They mostly go up in size (and price of course) from there (unless they are smaller than your former 42 inch TV... if you want or can use smaller, of course, that would save you $50 to $100 on the price for the TV I just referenced above, the 43 inch TV. And larger ones are higher in price and mostly too large for your alcover size, so here's the one other one listed by Harvey Norman that might do:
is listed as $1,044. It has 4 HDMI ports (that's plenty!) and some capabilities the formerly mentioned one doesn't have... and it is also 43 inch.
Let me know if I need to find more listings... and what you think. Thanks.