Hotpoint Aquarius DWF50 not cleaning properly

I wonder if anyone can help. I have had this dishwasher about 5 years and I have always had a few problems with not everything coming clean but used to assume it was just my loading techniques. However it has got worse and worse to the point where you almost have to wash everything before you put it in. I have tried different detergents, started using hotter wash programmes, putting less items in, everything I can think of and still half the load comes out still dirty.
Thank you in advance for any help anyone can give