I have been asked to look at this for you.
If the property is leasehold you would need the landlord’s consent. That is assuming the area is part of your lease. He would need to give consent for the work to go ahead and he would need to give consent for the application for planning permission. He is usually entitled to charge a fee for that and sometimes those fees can be quite high.
If the property is freehold or leasehold you are going to need building regulations approval and planning permission. That assumes there is no restrictive covenant preventing this development.
Start with getting an architect to draw up the plans in basic format to submit to get outline planning permission. If the outline planning permission is granted you can then spend the money on getting detailed plans drawn and submit those for approval.
Once you have detailed planning permission based upon the architects plans, you can then get quotes for doing the work.
You might want to use the architect to submit the application for planning permission and to project manage the whole job.
Even if you get planning permission and the work doesn’t go ahead for whatever reason, the property is worth more with the planning permission than without.
You have to have substantially started the work within 5 years of consent being granted otherwise the permission will lapse and you will be back to square one.
Can I clarify anything else for you?
I am happy to answer any specific points arising from this.
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