Yeah I'll get it pressure tested this week.
Had a BIG scare earlier this evening, but fortunately now, all is ok.
Someone on the peugeot forums suggested the possibility of head gasket failure, and that the usual sign of that is water in the oil, making a "mayonnaise type substance on the oil cap and dipstick" as he put it. I'd driven 6 miles to someone today and the 6 miles back. When home, I checked the dipstick based on what he said. But didn't expect this..> no oil! Let the car cool down for half an hour to see if oil would return to the sump and checked it again. Still no oil!

Not a single spec of it. I thought wtf, my mechanic had serviced the car and changed the oil on the 29th april, not 2 weeks ago, and he's been servicing it for years with no issues. So I thought oh great, coolant leak and now oil leak, maybe it is the head gasket. Looked at the road by my car and saw this lovely blue and green oil slick.
http://i.imgur.com/WCmFFAF.jpg
http://i.imgur.com/ivv7u4g.jpg
No dodgy engine sounds and no oil warning light so I checked it just in the nick of time.
Called the AA who discovered it was just the oil filter was leaking. I guess my mechanic let me down a bit this time. So he tightened it up, said it had stopped leaking and he drove us to a BP garage to buy oil. Bought a 4L bottle of Magnatec 10w-40 part synthetic for diesel and used up half of it. Checked for leaks again and it was fine. Phew! Seems like I drove the car to within an inch of the engine's life, and had I not checked, there's little doubt I would have blown the engine up tomorrow as I have to take my mum somewhere.
Topped up the water again while AA man was there and he told me to fill it a fait bit higher than that X stem in the middle. So far, no warning messages, but no doubt it'll return. I'm just so glad I checked the oil though. Also, by the colour of the oil on the road, the AA man is confident water hasn't gotten into the engine.