Trivial in the scheme of things but any supplier warranty on the boiler will be gone due to lack of servicing. The paving warranty may not be up to much either- you may find in the small print that the 10 years only applies to original purchaser. The drainage bit- have a chat with the neighbours & see where their rainwater goes, if its a clay area (where soakaways don't work) then the permeable surface argument gets a bit thin (plus if it was a refurb of existing hard standing then its all moot anyway)