well the only travelodge with a room on the saturday seems to be city centre for £66
ibis in the city centre is £56 for the saturday
holiday inn northampton is £54

then of course you start gettin silly prices like £100 for the hilton

you can share my room if you want, you have the bed and i'll grab the sofa
I warn you though, I snore

maybe someone else in the area has a spare room?