'one' and Stena offer cheap combined travel from Liverpool Street:
http://www.stenaline.co.uk/stena_line/stena_li ne_uk/harwich_-_holland/gb/rail_and_sail.html
However, since the withdrawal of the HSS fast ferry service, it's quite a long trip and the North Sea isn't always very 'user friendly' at this time of the year ;-)
Ryanair will fly you from Stansted to Eindhoven. There are no cheap fares out on Monday but you can fly out at 0655 (or 1705) on Tuesday for �5.99. Flights back on Thursday (at 0925 or 1935) or on Friday (at 0925) are priced at �0.01. The 1935 flight back on Friday is �14.99. Based on �5.99 out and �0.01 back, the full return price including taxes & charges is �41.19
http://www.ryanair.com/site/EN/
easyJet will fly you from Luton, Stansted or Gatwick to Amsterdam:
http://www.easyjet.com/en/book/index.asp
However, the prices are dearer than Ryanair, at roughly around �100 return inc T&C
Eurolines typically take around 12 hours to get to Amsterdam, from Victoria but they've got fares from around �20 one way:
http://www.nationalexpress.com/eurolines/home/ hp.cfm
For cheap accommodation (with customer reviews) go here
http://www.hostelworld.com/
and use the 'Additional search options' to select 'Guesthouses' and 'Budget hotels'.
Chris