What is the cheapest & best way to make a dumb tv into smart tv?

I have a dumb 42" TV & I want to make it into a smart TV, the cheapest & the best way, I'm in the UK.

Links, recommendations & what to stay away from welcome.

My friend swears by his Roku.

My daughter uses a Nintendo Wii.

I was hesitant to buy a smart TV because I didn't want the 'smart' frying and leaving me with a useless display - but the Samsung models I bought can operate as displays completely separate from their smart capability. The 42" one is better because the smart menu is available all the time, the smaller (30"?) one has to 'boot' into smart mode, but works perfectly once it loads.

Roku is good. Also bluray players with built-in Wi-Fi. But the most important thing you need is fast internet speed

A fast hookup is vital,
Rouko is fine i love it.
But a total brain over haul isn't worth it
Walmart just came out with a price break on the new smart t/v's

Ah, simple recommendations to add to the others are.always mute all commercials(brings welcome peace, eliminates loud, unwanted & unneeded irritating noises of ads), block channels which show stupid or boring programs, also record great shows such as good, educational and informative Nature and travel shows plus other good programs for viewing much later when nothing else is on.also, it may be possible to add a Kindle or other free book reading app. For times you may just like to sit back and read.These are very economical things to do.

Cheapest is probably a ChromeKey. This sells for $35 in the US. But you need a laptop, iPhone or Android phone to control it. (no remote is how they save money).

Next is the Western Digital TV Play box which sells for $70. This is my personal favorite. But you also need an HDMI cable.

Next is the Roku3 which sells for $99 - and you also need a HDMI cable.

Apple TV