Hi, I've been sending my transcript and LORs to LSAC since October, but nothing has been updated in my LSAC account. It looks like the two transcripts are lost in the post (they show through tracking as having got to the US postal service, but not delivered) and two LORs show through tracking as having been received, but aren't uploaded to LSAC.

For any UK applicants through LSAC - what address did you send your transcripts/LoRs to through Royal Mail for them to get there successfully? I've been using the address on the transcript request form, which has the postcode as 18940-8511; neither of my sent transcripts have been delivered when the postcode has been entered as 18940-8511 by Royal Mail. For my LoRs, I've always put the address that is on the transcript form, i.e. postcode 18940-8500; the two that show as having been delivered have had the postcode entered as 18940 by Royal Mail despite 18940-8500 being written on the envelope.

I'm resending my transcript for the third time and because of an urgent deadline I'll be doing so by a £50 courier delivery service to ensure it's there next day - because it seems like the address/postcode is problematic I'm wondering if anyone who has managed to successfully send transcripts via Royal Mail / Parcelforce could confirm exactly what address they put.

I sent my transcripts and some of my LORS through FedEx/UPS. I would suggest you to do the same. Enter the exact adress as written on LSAC site, it will surely be delivered.
If you know for sure that the LORs have been received by LSAC but they were not processed, you just need to be sure that you send the accompanying form with it.

If you sent the form with the LOR, they will process it after couple of days since the receipt. (it's LSAC's peak time right now).