I haven't been in the T5 arrival lounge, but if the shower rooms are the same as the ones in the T5 departure lounges, I much prefer the AA shower rooms.

I'm about to do the HKG-LHR flight soon that arrives into LHR around 0630. Flying Y as OWE. Do I have any arrivals access? It'd be nice to shower and change.

You will have access to the AA arrival lounge.

Confirming what others have said. BA LHR T5 has THE best arrival lounges - full English/continental breakfast, masses of space, newspapers, Elemis spa and products, waiter service and separate room for F passengers (who also get cabanas with infinity baths) BUT, although there are loads of them so it is rare to queue, the showers are woeful. CX HKG arrival lounge has great showers but too few of them - last time I went there, I queued for an hour and then gave up and went home (original plan was to shower and change and go straight to the office) and the food offering is AWFUL - truly dreadful. AA arrival lounge at LHR (used by CX for certain flights) is in the middle - nothing stellar, nothing awful. Enough space for the traffic they get, decent showers (towels could be better, but quite acceptable), pressing service which works surprisingly well, and enough in the way of a decent hot/continental breakfast offering to satisfy without being overly special.

I would use BA and AA Arrival lounges in LHR every time UNLESS I was time-constrained. CX HKG arrival I would use ONLY if I was time-constrained.

Given the effort CX make with their other lounges (except G16, which is awful), The Arrival is (or should be) quite an embarrassment

Really ?
A few years ago, a CX staff in HKG could not issue an invitation for the arrival lounge, because of I was flying Y as CX DM.
At least, the system could not issue an invitation. So, I didn't try, went to a Priority Pass lounge.

Yes, you do get access. Just show them your card. It's only the passenger that's allowed in this case.

So I should try to go to BA or AA first. Does the CX flight arrive in T5 though?

Also is there luggage storage after collecting it/clearing customs?

Flight arrives in T3 so you will only be able to go to the AA arrivals lounge in T3.

Which flights are you taking? Only the two morning arrivals can get access.

I'm now taking the 9am HKG departure which I think arrives around 2 or 3pm from memory. Do I get access and is there any guest allowance?

You won't have access to the Arrival Lounge at T3 as only pax arriving into LHR in early morning get to use the Arrival Lounge. I think the lounge actually closes at 2 or 3pm.

HKGglobaltrotter answered the first part. Anyway, the term of use for an arrival lounge is:
"Available to members arriving in Hong Kong, London (CX 251 or CX 255 only) or Frankfurt on flights marketed and operated by Cathay Pacific or Dragonair. Admission is for the day of arrival and guests are not allowed. To facilitate access to the London Arrival lounge, members should obtain an invitation card at their point of origin."
I hope this clarifies all questions on arrival lounge accesses.

Not according to the rules for both cases. While EMDs can get access to The Arrival at HKG if arriving from a CX / KA FLT, this does not apply to the arrival lounges at LHR and FRA, which is for CX DMs and GOs only. See http://www.cathaypacific.com/cx/en_H...tance.LHR.html.

Do be sure to do this. I didn't and had to do some fast talking and web-page loading to get into the AA arrivals lounge last time I was at LHR. Got in eventually

I checked my flight.
It was CX251, 5 years ago.
Maybe, a rule has changed.