Hola Dan and Steven. Thank you for your comments. What you have said agrees 100% with my understanding. However, there's a minor snag - RS Lesson 1.10 gives (under one of the Por ejemplo sections) the example:
Me gustaría unas camisetas nuevas.
Doh! Perhaps we haven't got to the bottom of this yet! After posting this question to this forum, I attended a Spanish class and asked our teacher (who is a native Spanish speaker from Peru) about it. I only got a partial answer and so I need to talk some more with her next week. She said somewhat vaguely that both (gustaría and gustarían) could be correct! Doh! However, she did draw a distinction between:
Me gustan las camisetas,
where the speaker is expressing that he/she likes the specific T-shirt things that he/she is referring to and:
Me gustaría / gustarían unas camisetas nuevas,
in which he/she expresses a wish to obtain some (non-specific) new ones. Does this mean that the rules are different? I don't know!!
Interesting additional information, maybe, but I still can't satisfactorily explain "Me gustaría unas camisetas nuevas" to myself.
Grateful for any further thoughts.