Things that are bothering me or relate to what's being discussed here.
Cassie said that if she didn't complete the outstanding three months' service to get to the 30 year benchmark, she'd lose £124,000. John said they'd be ok and would manage wherever they're supposed to relocate to with his job, Cornwall? but Cassie said she didn't know how much money was going to be needed for her father's care. So at first she had to go back for the cash shortfall and then stay despite what John said, because she wants to solve the case.
The victim's body. Matthew Walsh's torso was found in a freezer at Robert Fogarty's home after he too died. The skin displayed signs of 'freezer burn' When the head and hands were discovered in the unchilled freezer cabinet in the storage unit, they were mummified, so not frozen despite being located in a freezer. Who mummified them and where had they been kept until Fogarty acquired the storage unit, was it him paying the rent? He could've taken the remains there at any time in the last eight years.
The fountain pen in the skull. Not any fountain pen, a very expensive one engraved with a serial number, which might point to a gift for Liz when she graduated university (Oxford?) Possibly a more likely scenario than a gift for passing out at Hendon especially seeing as none of the five had any family or friends attending.
Will detectives be able to trace that serial number and record of sale?
Also noted that the pen had a gold nib, which is not a hard metal and especially not so for a weapon.
I don't think Dean's past criminal activity is to do with his brothers, He changed his name and address and didn't want to be found. Just who did disclose his home location to his mother? I can't see it being either Cassie or Sunny.
I think Fiona's version of events is very suspect, far too keen to drop everything on Ram. I'm not clear about Ram's father, is he simply ignoring Ram or does he have some kind of dementia too, he didn't seem to speak to his wife and I can't recall any more about him.
Fiona lies about everything, literally everything. I really can't figure if the children are hers or just her partners, I got that impression, but it's not clear at all is it. Ram cheats and lies, right from when we first saw him parking illegally and tipping the wink to the traffic warden near the family business. He misused the police computer, destroyed the credibility of the complainant against him and is involved with something shady with Dean. Liz and Dean were supposedly the brightest graduates of their group from Hendon with Dean being the most naturally predisposed to police work according to the trainer. Who and what has he been involved with in the past, who did he owe a favour to and how is Ram implicated in that?
When Liz threatened her mother that she'd put a pillow over her as she slept she was extremely menacing and I believed she could do it too.
The ending was such a cliff-hanger. Presumably Liz was on her way back from East Anglia where Cassie and Sunny had interviewed her? hence her being in a car. We don't know the time frame really do we and I can't see how anyone would've been able to place Cassie at that junction at that precise time.
I think the women are my chief suspects, can't decide which one yet, but I bet there's a massive twist and we've all been puzzling our brains over red herrings. I've got more but have gone on far too long 
The mummification is the big question though, that's hardly been brought up as a query.