by the sounds of it with the astra you might be needing a replacement motor (about 3.5k for a brand new one + fitting)
as for the pulsar. depending how much damage has been done you could easily be looking at 2k for fixing it up (presuming radiator and head need replacing)
maybe get a quote on what it would take to fix the pulsar and see if you can get financial help from a relative as trading in the astra on the repairs would in the longer term be a loss.