a landfill or scrappy wont have an totally accurate reading. possibly to within 50kg as every car ive scrapped has always been a round figure of 1150 or 1200 etc. i think most weigh bridges will under read as well to scam you of some money.you wont get anything other than total car weight either.
i could give you a name and number but itll be about 200 miles+ from you. any local tuners that lean towards racing and tuning will be able to point you in the right direction.