LHR - LAX - LHR Virgin Atlantic Novice - any hints & tips?

Hi – I hope this is posted in the right place?
I will be a lone female flying to LA & back at the end of Feb, PE on VS23 and return on VS08. It’s been 18 years since I last flew Virgin and have only been long haul a couple of times on package holidays in that time, (we usually stick to Europe ).
I’m not a great flyer, so I’m a little apprehensive and trying to do lots of research to makes sure I’m as prepared as I can be, I wonder if anyone can give any hints or tips for this particular journey that will help and I’m also curious on the following…
• Is there any benefit for / against checking in on line vs checking in at the airport?
• If I check in on line, do PE get a priority bag drop at LHR or will I need to allow extra time to queue?
• How long should I allow for security at LHR, I can’t seem to find any option for priority lane access like at smaller regional airports.
• I’ve reserved seat 25D both ways (there wasn’t a lot to choose from)– any thoughts? Should I try to get moved ? If so, where to?
• Depending on what reviews I read some mention a PE amenity kit, and some mention the lack of one. Is this standard? What will be in it that I don’t need to worry about putting in my hand luggage?
• Finally, not particularly bothered about an upgrade to UC, but just wondered if there is potential for this? I’ve been told by friends to dress smart – is that right ?

Thanks so much for your time & patience!!!

• Check in online - if the flight is overbooked and given you don’t have a loyalty status, you could be on a list of potential downgrades
• PE get dedicated bag drop
- PE don’t get priority security - it’s fairly efficient, allow 30 mins but you could be through in 5!
• I’d try for a window seat at check in but it’s personal preference!
• Amenity kits in PE are only on overnight flight, not day flights! Standard toothbrush etc - nothing amazing!
• If you want to be in UC, you’ll need to ask if there’s availability and pay their asking price on the day! In the unlikely event they have to OpUp someone, it will be a gold member who is given priority so don’t think by dressing nice it will have any benefit!

I'd comment I have had an op-up back in the distant past when I was a lowly Red member from PE to UC. Therefore I can confirm It does happen, and I was dressed smartly, but I really doubt that had an impact. The flight was full (overbooked) in economy and PE, so it does happen. Nowadays it's more likely full in PE and UC, and empty in economy on the routes I've taken recently. (Last flight was a 50 person economy load, to a full PE/UC).

In seriousness though op-ups are very very rare, and if you want to be in UC, try to negotiate it on day - and if you have enough miles and an upgradable class of ticket (more common now in PE) - you can try this ahead of time. If not, collect the miles for next time, upgrades from PE to UC can be reasonably easy, and are a reasonably good use of miles in this posters opinion at least. Many of us upgrade in this way a fair amount.

I would also comment that either flight upgraded would be great, the clubhouse at LAX is one of the best in the network - the food there is amazingly good.

Thanks both for your responses.
An upgrade, whilst lovely and wouldn't be refused, is way down my list of priorities. Just getting through the LHR, on and off the plane and out the other side with my baggage will be a big win for someone who rarely travels alone hence, all the questions!

The "dress smartly for an upgrade" idea comes from many years ago when, on overbooked flights, check-in agents would be told to mark suitable passengers as SFU (Suitable for upgrade) in the check-in system so that "the right sort" could be selected to sit in a higher class. This no longer happens.

Nowadays, passenger profiling is a science. The airline knows how often you travel, how much you spend, where you travel to, how you redeem your miles and a hundred other things. Upgrades are now decided in advance by an algorithm - the only exception to this (that I know of) is for service recovery.

By all means dress smartly but comfort is king!