JMcMillan wrote:But it doesn't give the bearer or his descendants a seat in the Spanish parliament. The inherited seat in the House of Lords was why the UK stopped creating heritable peerages, wasn't it?
You are right that Spanish lords do not have seats in the Senate (Senado). When this ceased to be the case I do not know, but it may have been as eraly as the pre-Franco republic.
Only 92 British hereditary peers now sit in the House of Lords, 90 are chosen by a vote of all the hereditary peers and 2 are ex officio. The number of life peers is now ridiculously large, leading to calls for life peers to be members of the House of Lords for only a limited time.