It depends upon
which TV services you want then, Melv.
As I stated above, the Humax box in Zac's link only offers a few apps, providing Youtube, BBC iPlaye, etc. It doesn't provide any additional broadcast channels.
If you've got a 'non-smart' TV, a Now TV box (for just £15) will make it 'smart', providing you with all of these apps:
http://web.static.nowtv.com/email-marketing/assets/legals/NOW_TV_apps_21AUG2015.pdf
However in order to get additional mainstream channels through a Now TV box you have to pay for them. There's no minimum contract involved though; you can stop and start your subscription(s) whenever you want.
For example, £7 per month gets you the Entertainment Pass, giving you access to Gold, Sky 1, Sky Atlantic, Sky Living, Sky Arts, Fox, ITV Encore, Comedy Central, MTV, ABC Studios, Nat Geo and the Discovery Channel. (There are introductory offers available as well, giving you the box and three months access to those channels for £25 or the box and 6 months access for £40).
There are also passes available for full access to all Sky Sports channels (except pay-per-view events, such as world title boxing matches) and to 11 Sky cinema channels., as well as one for 6 kids' channels. So you can pay for only the type of TV channels which you're likely to watch.
(Confusing, given that the ordinary Now TV box is already 'smart', there's also a Now TV Smart box available, for £25 more, which gives you access to Freeview channels via the internet and also allows you to pause and rewind live TV).
http://www.nowtv.com/tv-boxes
Another possibility is an Amazon Fire stick but it's mainly used to access premium paid services such as Netflix and Amazon's own content:
http://tinyurl.com/gvvmmna
However, whatever type of device you decide to go with, you won't get any (watchable) additional TV channels for free via the internet. (There are hundreds of free channels out there but not many people want to watch US evangelists preaching or the parliaments of obscure countries in session. You have to pay for anything worth watching!). The only exception is if you purchase a 'fully loaded' Kodi box, which can be used to access loads of subscription-only services without charge. However they're
(a) difficult to use if you're not technically minded ; and
(b) totally illegal!