You will have to pay your solicitor and valuer for their time.  From the date you give notice claiming a new lease, you also have to pay the landlord’s legal costs, plus the landlord’s valuer’s fee for the initial valuation, whether or not the new lease completes. So, if you change your mind, you will have to pay your own solicitor’s and valuer’s costs plus the landlord’s wasted costs and initial valuation fee.  The landlord’s costs you have to pay are, however, limited to the costs incurred in responding to your claim and preparing a new lease. You do not have to pay your landlord’s valuer’s costs of any negotiations with your valuer, for example (although obviously you do have to pay your own valuer’s costs in respect of those negotiations).