Just an update on my post.

SQ LHR has reverted to the old rules. You are not allowed up to 25KG in Y and 7KG in hand luggage. The hand luggage allowance is no longer transferrable to your checked baggage.

Very Very unofficially, you are allowed up to 30KG in Y. I hypothesise that this would be allowed if you're travelling for a month as a tourist or something like that. Anything about 30KG in Y per person is strictly charged at the respective baggage allowance charge.