oil pressure light is coming on

Hi. Seems I'm too new to create a post, so replying to this existing one, hope that's OK
I've just done a ton of work on a relative's 2006 C3 1.1 - new valves required after cambelt lost some teeth....Changed filters and oil whilst I was at it.
Anyway it started up again no problem and sounds good. But the oil pressure dash light keep coming on, with a beep. Stays on for a second or two, then off for 5 to 10 seconds, then back on. Checked the level and it's fine. Doubt the oil pump is worn out at 65000 miles.
But I'm not sure about the oil filter and its housing, so wondering if that could be the cause. It has the shorter fatter filter, with no 'prong'. Inside the cap there are 4 small lugs or tabs that look like something should be clipped into them. But nothing was.
In the housing there is a plastic tower that fits inside the paper cartridge. It has a light-ish spring inside of it. But there is also a stronger spring sitting loosely around this tower.
Is this all normal? Because it doesn't seem right. Especially the lugs inside the cap. Seems the top surface of the filter just presses against them, bare, which is not going to form a seal. Possible the strong spring was added to try to get a seal? I've ordered a new cap which has a downward pointing tower inside, which will fit into the filter, with a flat area surrounding the tower to allow sealing. Which seems a lot more sensible.
But should I retain the strong spring? Or is this an interloper than I can ditch?
Many thanks in advance for any and all advice
Joolz

Despite owning 1.6i and 1.4i (TU5 and TU3 engines) I have not investigated this further. But while the oil filter housings look identical, they have different types of filters.
The TU5JP4 (1.6) engine has the short filter, without the "prong" on it and the TU3JP has the tall filter with the prong. I am not sure (as I have not compared them) but I think the black oil filter housing caps might also be different to accommodate the different filter types. The 1.1 (TU1) engines are practically the same as the 1.4 (TU3) engines.
So, I believe the short filters are for the 1.6 engines and the tall filters are for the 1.4/1.1 engines. My guess is the oil pumps are the same but the 1.4 and 1.1 have a lower flow but higher oil pump pressure (because of the prong on the filter). I guess the 1.6's oil pressure is lower but a higher flow? Consequently, I would recommend trying the tall filter, with the prong, in your engine.

If you supply your VIN (and ask nicely) I think Arfur can supply the correct part number for your oil filter and that will settle it.