Installed a modest conservatory on a large deck some years ago, having previously talked to managing agents. Am now thinking of selling and was advised to seek "retrospective permission" from freeholder for a nominal fee. Has anyone encountered this problem?
You say you consulted the managing agents, and I would have expected them to suggest that you contact the freeholder to check if you needed permission. In certain circumstances leaseholders require a Licence for Alterations from the freeholder, subject to the sort of the work they want to undertake. Among other things the Licence indemnifies the freeholder should things go wrong with the work, any disputes with neighbours arise or Building Regs are not complied with. As far as I know the fee for a Licence can cost around £500.
Over cautious it may seem, but the problem could be that even if it's a 'modest' conservatory, if it's attached to the exterior wall of the building any buyers solicitor may want proof that the freeholder granted permission for you to do this.