If you sell within 3 years of moving out there will be no CGT to pay (normally) but again ensure you check as tax law changes at the whim of idiot governments..
Also worthwhile getting the property fully valued before renting out as if you bought it 20 years ago the value may have gone up but provided it is a legitimate valuation then HMRC are more likely to accept it.
Interest on mortgage is allowable but again if you have low mortgage then remortgaging before moving out and taking equity out is allowable providing done before 1st let out.
There is a 10% allowance for wear and tear with fully furnished but avoid FF like the plague as little premium in rental and tenants will thrash Furniture.
Get Gas / Elec fully checked and sorted before tenants move in and take every single electrical item other than built in items out as you responsible for PAC checks every year on things like Kettles / TV etc etc