engine noisy/rough

ok, so when i bought Carly (my 08 plate cooper) about a year ago, after two months (and after reading about the problems on here!) i got the timing chain and guides changed as it sounded ratly. that was around 8months ago. noticed yesterday that if when stationary ihold the revs at around 2000 rpm, the engine sounds rattly, kinda knocky if you know what i mean. Just sounds really rough! rev it ul, sound gies away, although still sounds course/rough.

there isnt any loss of power or anything, but did notice the oil was low so topped it up with correct oil. engine still sounds really noisy. also noticed on tick over, its really "ticky".

hoping it isnt anything serious, but have to say compared with all the other cars ive owned over the years, i feel the mini engine is probably the most unrefined and course engine ive had. any ideas what the prob might be? shes only done 66 thousand miles so not high miles