Bazaars, ferries and serious food
Tap water is chlorinated but NOT recommended for drinking — bottled water is the norm (cheap, everywhere). Fine for brushing teeth.
~5–10% in restaurants if service isn't included; round up taxis; small tips for hotel staff and the hamam. More than Italy, nothing like the US.
Drive on the right. Istanbul traffic is notorious and bridge/tunnel tolls run on HGS. Cities have excellent transit — a car only makes sense for coastal touring.
Your UK plan won't treat Turkey like the EU — check roaming rates or use a travel eSIM. Local Turkish SIMs are fine for holidays; Turkey only blocks unregistered foreign phones after about 4 months in the country, which no tourist will hit.
sourced — translations from published sources; corrections come from user reports
Free to start. iPhone first — Android close behind.