I think I need to start from the beginning of my water slushing saga.
In July of last year, I noted a gurgling sound on starting the enging up. I obviously took it to the garage who informed me that my engine coolant level was low and they topped it up for. They also did a pressure test on the coolant to make sure that it wasn't leaking - which is wasnt, and all was well again. About six weeks later, I noticed the same noise on starting the enging. So I took the car back to the garage, at this point I had also noted that the passenger footwell was damp, my car was then diagnosed with a leaking heater matrix (thankfully this was covered under warranty). So I duly booked my car in for two days later on that week. I happened to be going on holiday the following week so I said that I would leave my car with them for the week for them to sort out. It turned out that the matrix they fitted was a modified one and now meant that if it was to leak, it would like outside the vehicle and not into the vehicle - does that sound right? I have had a number issues with this garage, which I shall not name for the time being.
Anyway after having my car for well over a week, it still gurgled on starting but the Technicians informed me that this could simply be due to air in the system as they had pressure filled the coolant ????. All was well for a good while until October last year, when I noticed the swishing on going round corners, obviously assuming that this was something to do with the matrix I took it straight back to the garage (and was obviously quite frustrated at this point), but it turned out to be a blocked duck bill

, but I noticed it again in December - which is when I posted here, but the problem seemed to dissipate. Now it seems to be swishing again on going round corners - this morning it was noticeable on going left!
Could this be that air is still working its way out of the system. The coolant holder is quite hard to see so it is difficult to ascertain whether this has gone down or not.
I am getting really frustrated with this particular garage as customer service does not seem to be a big thing in their service department, and nothing is ever explained to you properly. I don't want to feel like a nuisance customer.