Just to update (in case anyone is looking for this info in the future), here is what I did:
* Spoke to Citizens' Advice (very helpful in general - FYI, you can only contact them through an "076" non-geographical number [therefore not covered in most fixed or mobile price plans] - however, they will call you back if unavailable. This is handy, as it's up to 35c/min otherwise from a mobile, depending on your service provider!)
* Went in to SW office. You take a ticket and wait. Very friendly - made appointment for the following week and outlined what was required to bring in.
* On the day of the appointment, brought a completed form, proof of address (a bill), photo ID (driving license) and birth cert [which I didn't need in the end]. Again, the "deciding officer" was a lovely woman who was very helpful.
* Got a temporary SW card to use to collect money from post office. This was set up to "time out" when I start my new job.
* Clarified that, aside from being entitled to SW while out of work for this brief period, it was a good idea, as a gap in PRSI contributions may have otherwise affected pension entitlements down the line.
All in all, not as daunting an experience as I expected!