So I took the advice and phoned around...
Aviva: online quote 8 euros more expensive than broker quote i.e. about 14-15% up on last year. Refused to speak to me on the phone because I have previously dealt with a broker. Would not permit any complaint to be made about this or about the price hike. Unimpressed.
Zurich: Would not quote for subsidence cover within the policy. What??? I live in South Cork. I don't believe there have been any landslides or earthquakes here recently... The house has stood here for over a hundred years and hasn't subsided yet so pretty unlikely. I thought this would be the cheapest as I also have motor insurance with Zurich. I think the agent probably messed up the quotation? Or else their database is severely out of whack.
Allianz: could not complete quote process online. Hopeless telephone agent who could not retrieve the quote to find out why and did not know what to do, then the fire alarm went off in their call centre so could not complete the process.
Liberty: Could not complete the quote online. Extremely noisy call centre and agent with close to impenetrable NI accent but very patient. Quote 33% MORE than Aviva. Did find out that a stone and slate house is regarded as "standard" construction if you get asked that question.
FBD:Could not complete the quote online. Terrible hold music but excellent agent. Quote 17% CHEAPER than Aviva and roughly the same as what I paid Aviva 2 years ago. Only company that asked any questions about the house (when last reroofed, when last plumbed, when last rewired).
Now off to ask my broker how come they couldn't have found this out?
NB the Google search results suggest three of these companies use the same call centre on contract for their policy sales (Abtran). Moral of the story: shop around guys...