no dont use ketchup , ketchup will probably give the salan a meetha sa and ketchup taste . it wont blend into the whole masala taste , you will be able to tell you have used ketchup.
however sometimes when i make pasta i do tend to add ketchup to the sauce when i have less or just to give it a taste ,it works well there but i dont think it will work in a salan.
i have never tried it though. tinned tomatoes are available at every grocery store ( tesco , asda , even some asian stores ) .
also to make cooking more easy you get ready made lassan and garlic paste and fried onions - although i have never used them they might help you. ( so next time your watching starplus and zee pay attention to all those song like adverts on spices , onions , chawal , atta and besan hahahahaha )
good luck .