Spending £200 on a wheel upgrade for a £450 bike is a waste of good money. It certainly won't make it a £650 bike.
If you haven't got any, use half of that money to get yourself spd pedals and a pair of (MTB) cycling shoes that you can walk in. Spend the rest on other bike-specific gear and clothes. Then ride that bike into the ground while saving up for a nicer one.
Just had a search for that bike which resulted in some confusion. One spec has it down as a 28 spoke, but I can only count 24 in the pic. If it really is 24, then you're past the line where rider weight can certainly be an issue, which might indeed be a reason to look for another wheel set (while cursing the man and the store that sold you unsuitable gear in the first place).
Another spec has it down as using 32 spoke wheels, which are fine for most people and uses.
Here's a rear wheel that looks to be stronger. Fronts are inherently stronger and carry less loads, so they're usually OK anyway.
If you think it's important with a matched set,
here's a pair. Be warned though, the spec doesn't tell which spoke count it is, and I'm not sure if it's the pair in the pic you'll be getting.