I bought this travel system in a hurry (possibly regretting!) and wondered if people had any experience / could advise on the bassinet setting please as my brain won't work it out - it's one which converts from Bassinet to a normal pushchair seat. It comes with a carrycot mattress. Are you supposed to keep the straps for the pushchair setting in and then just put the mattress on top (in which case isn't it a bit lumpy under the mattress), or strap the baby in (in which case where does the mattress go? Not my first but my previous carry cot seemed more user friendly. TIA