In the sentence above, if I change "I should like" to "I would like", will there be a noticeable difference in the meaning or nuance?
There would be three differences in nuance, based on:
- The character, and indeed his entire culture, is meant to be quite old-fashioned in many ways, even within the context of the story.
- Though failing to do so (the joke went flat and struck many there as rude, if I remember the story right) he was aiming at polite speech, in a moderately formal register.
- The character is a member of a culture that the author based on all he felt was good about rural England.
Each of these impressions are helped by the choice of should over would in a few different contexts being more often made in the past, than now, in England, than elsewhere, and in it being considered the more polite expression by some.
The association with politeness can led to anxiety in certain quarters, and those with nationality have meant that there were complaints about how the Scots and Irish failed to use it correctly in the days when the expense of trans-Atlantic travel meant one would rarely have the opportunity to complain about it in Americans.
Luckily, it being seen as old fashioned means we need worry less. (Though not that old fashioned, you wouldn't see Chaucer use it).
Fowler described the usage of southern Englishmen as so complicated that nobody not born to it could hope to understand it.
A common rule suggested, is that in the cases where either can be used, then normally shall/should is used in the first person and will/would in the second and third, unless one wants to stress particular determination in which case this is reversed.
And if we believe that, we have to believe that Churchill wasn't particularly determined when he said "We shall fight them on the beaches" and would have taken military defeat with philosophical calm.
Those of us who use it, tend to do use shall or should in places where will or would could serve, tend to do so inconsitently and idiosyncratically, as a result of having had teachers, parents and books making inconsistent and oft-times idiosyncratic attempts to teach us the proper way to do something no-one was sure of the proper way of.
Really, you will fare fine using would and will in such cases. Unless perhaps if you are writing fiction (Bilbo should totally use should that way, a hard-bitten cyberpunk detective in 23rd Century Kyoto, not so much). If nothing else, ambiguous uses can be worse with should:
In his sermon, the priest said we should all sin a lot over the course of our lives.