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Yes, presuming the external demise changed. You can move things around inside all you like and they don't care.
Our buyer's conveyancing solicitor was great (we now recommend her to people, not our own...) and possibly less good conveyancers wouldn't have spotted it, but not a risk I'd want to take given the very small cost of submitting updated plans to the Land Registry.
Also this was a shared freehold flat, if it was freehold house I'm not sure it would matter (but I don't think I'll take the chance now we own one and are planning to extend).
Don't forget to budget for all the little things that add up. Some real life examples from my spreadsheet last time we moved:
YMMV of course. Don't forget all the possible conveyancing charges. You know, things like leasehold supplement, ID & anti-money laundering checks, financial transaction fees, Land Registry fee, file storage, mortgage fee, authentication of buyer's lawyers, VAT on legal charges...
Your conveyancer may well 'forget' to detail all of these in advance. Good luck!