The short answer to your question is No, there won't be any conflict. The aerial connection should loop through the Youview box to the TV. When watching Youview you will switch to one of the TVs AV inputs (HDMI or SCART). When watching the TV's own Freeview tuner then you'll switch to DTV on the TV.
[TIP: Don't use the cheap moulded aerial coax fly leads
such as this; they are poorly shielded and are often the first cause of interference and signal loss problems with TVs.
Buy some proper TV coax (Webro WF100, or Raydex CT100, or Triax TX100) and a couple of coax plugs. There are plenty of online guides of how to fit plugs. No matter which method you use, as long as you follow the method then your coax lead will be massively better than the moulded type fly leads.
]
As for the TV, it's a long time since Toshiba made their own TVs. The same goes for lots of once-independent brands. The rights to use the badge were sold off, and now one of the three faceless manufacturing giants produce all but a handful of key brands. The Technika you are considering comes out of the same type of factory that produces Polaroid, Techwood, Bush, Techwood, Alba, JMB, Digihome, Goodmans, Luxor, Blaupunkt, Dual, Wharfedale and dozens of other brand names that sound vaguely familiar. The same goes for Hitachi, Sharp, Sanyo, JVC, etc.
Since nearly all are now made by Vestel or TPV etc then it's tempting to think that they'll all be the same quality and performance, but that's not the case in my experience. There's still a difference with some brands in picture performance. I have a 32" HD Ready Sharp in the house that knocks spots off the 1080p budget brand TVs I often come across when installing for customers.
The only brands where you're reasonably assured that it's made by the company whose badge is on the front are Samsung, Panasonic, Sony and LG. I say reasonably because both all of them have at one time or other used 3rd party major components such as screens or gone to other companies to have their products made under licence.
Bear in mind with reviews, and especially with buyer-written reviews of budget products, that their experience and expectations may be limited, and that they're often writing in the honeymoon period after buying a product when they're still in awe of this new shiny thing.