conditional constructions - "Should" instead of "were to"

Can we use "should" instead of "were to" and vice versa? I've noticed that mostly they mean the same thing in the subjunctive and the conditional clauses. Especially when the "were to" isn't in the if-clause but an inverse conditional clause instead.

What I mean to say is that these mean the same:

• Should we get more money next month, we would be able to buy an oven.


• Were we to get more money next month, we would be able to buy an oven.

But my British friend says that "should + would" is incorrect grammar and "will" should be used instead. I cannot find a way to prove that my examples are correct. And he says the inversion is too formal and best be avoided. His variants are:

• If we should get more money next month, we will be able to buy an oven.


• If we were to get more money next month, we would be able to buy an oven.

That makes them completely different in meaning.