What do you mean by blotchy screen? I'm assuming that the picture is breaking up or pixelating. If so check your signal quality & strength in Settings.
Ideally a strength of approx 90% & quality at 100% is what you want to see.
Tried a channel that it normally does it on and it’s 95% so that’s fine,and yes it’s Pixelating and breaking up,only does it every now and again ? Thanks
It might just be that the 95/96% strength is just a little too high for the unit's tuners.
If this is the case - and very often is - then an attenuator fitted between the aerial cable and the aerial input on the unit.
You would be best getting something like "Variable Signal Attenuator with Line Socket Input and Output" for about £4 delivered off of ebay. With this you can adjust it so that the input signal strength drops to say 90% to resolve the problem.