Welcome aboard Colin.
Falken 452's are a decent mid range budget tyre (imo) and it's what I used to have on my car before moving on to the newer version, the 453's. The problem will be though that mismatched tyres front to rear or side to side is never a good idea as it can unbalance the car.
The reason being that different tread patterns on the tyres, wear rates, grip levels/traction etc can all be different between tyres/manufacturers so will affect stability & control.
It's definitely better, sorry I mean safer, to have all four tyres from the same manufacturer/brand/model so probably best to change when you can although as long as you're not driving like a complete lunatic I doubt it will cause you any immediate problems but it is something to think about doing when you can.