If the car is tidy you could see £500+ for the whole car.
Might be worth more in parts if you have time and space to strip it and ship the parts.
Good running engines sell for £300+ from the breakers, more if servicing and repairs like timing chains/belts have been done.
1.8 conversion kits sell for around £500 alone.
Also depends what part of the country you are in? further north you go prices drop.
There are a lot of variables to consider before deciding whether to sell the car as a whole or break down for parts. If you have to hire stuff to lift out the engine you might see any gains evaporate and then have a long time staring at a hulk as other parts slowly make their way. If you're thinking of selling the car off whole and wondering if a 68k engine is a selling point, the answer is yes. As z22se points out, where I am in the NW it's easy to get around and lots of old cars are up for sale so prices get depressed. Peps in Suffolk has sold cars on at prices that I would be unlikely to see in my area.
Colour makes a play, too, because of the cost of spraying. If it's Star Silver or Sapphire Black then panels are everywhere but a less common colour might perk interest if someone's looking for them. More info from you would help gauge it - a couple of pics, engine type, rough location (don't show off your reg plate and home town as you might suddenly get tickets for speeding and parking that have nothing to do with you).