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Good morning, you simply need to address your intentions to the remaining co-freeholders. Keep all correspondence in writing so that everything is held on record. You should state what you intend to do, and ask if anyone has any objections. If they do they will stipulate, otherwise if they are in agreement keep on record their written consent to the works (to provide as evidence for any future sale). Hope this helps?
No, the lease does not need to be changed and you do not need a solicitor. Just written consent from all co-freeholders. Hope this was helpful. If you could leave me a rating then Just Answer will credit me for assisting you today. Many thanks