The UK do not have the same system as the USA so you cannot get traffic to interface and show on a Garmin 430.
As for the PCAS. There are times when it can be very useful. However I used to get occasional "ghost" aircraft where a warning would pop up quite close and appear to formate on me then disappear.
The PCAS altitude of the other aircraft is usually very accurate. The distance is not always accurate as PCAS uses a different system to establish distance and if the other plane's transponder aerial is dirty it gives an erroneous distance readout.
The verbal warning is just loud enough to hear when wearing headphones.
PCAS only gives 3 clues about the other aircraft. They are distance in nm, how many 1000s of feet above or below and if the aircraft is climbing or descending. The PCAS will give you traffic advisory if the other aircraft is getting closer and a resolution advisory if it is a serious threat. It is also quite intuitive to work out yourself i.e if other traffic is shown as 2 miles away, 300 feet above and the distance becomes 2.2 miles you are diverging, not a problem. However if it is 100 feet above, pops up at 3 nm and the distance decreases very rapidly he is probably coming head on.
There is nothing quite like looking out of the window and one should not use PCAS instead of that. I have had 2 instances where the PCAS warned me in advance of aircraft which I then saw and had to take avoiding action otherwise I would have come very close.
I have also flown in very busy airspace where the PCAS was going off continuously and I switched it off.
So my summary would be PCAS is not perfect but it is a very useful bit of kit especially in poor vis. It does not stop you from hitting non transponder equipped aircraft!