But he was familiar with London. King's X to Oxford Street is quite straightforward.
I can remember back in the 70s & early 80s growing up in the UK in Sussex, & living in London for a few years, it was common knowledge that Tottenham Court Road was the place to go, for purchasing discounted stereo hi fi systems, electronic gadgets etc.
So, all Andrew had to do was walk out of Kings Cross Station & turn right into Euston Road, keep walking until he got to the Northern end of Tottenham Court Road.
Oxford street begins at the southern end of Tottenham Court Road; he could have walked down the whole of T/C road checking out the best prices, then strolled into Oxford Street had a bite to eat at Pizza Hut prior to purchasing the Play Station.
I would imagine anyone serving him in the store selling the Play Station would remember him, given his distinctive tea shirt.
Someone could have initiated a conversation with him and lured him back to a nearby property.