Loads of reasonably priced B+B's in the Horley area of Massetts and Church Road, just a few examples:
The Corner House Hotel
72 Massetts Road
Horley
Surrey
RH6 7ED
Tel: 01293 784574
Fax: 01293 784620
Single
from £35.00
Double
from £57.00
Rosemead Guest House
19 Church Road
Gatwick
Horley
Surrey
RH6 7EY
Tel: 01293 784965
Fax: 01293 430547
Single
from £34.00
Double
from £50.00
Vulcan Lodge Guest House
27 Massetts Road
Horley
Gatwick
Surrey
RH6 7DQ
Tel: 01293 771522
Fax: 01293 775376
Single
from £36.00
Double
from £55.00
or try Ibis Hotel down the A23 (5 min drive from Aviation House) or the Gatwick Manor, both are travel lodge type's priced around the £40 mark...
Good luck!