VS,
Try the Train.
The Station at Luton Airport is a very short bus ride, about 5 minutes and it's FREE!!!!
Buses go from outside the Terminal frequently.
Then jump on the Thameslink (0345 484950)....it goes through London Village so it'll take about 1.30 but it stops at LGW...then the free CAA bus service to Aviation House which I think is every half hour from the South terminal, under the tunnel, opposite end to Concorde House.
Hope this helps,
Cheers
007
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