It will work in Spain and Netherlands, as long as the sim is still active and you have credit. With Vodafone Data Traveller the cost will be £2/day for 25MB/day, or £10/month.
Vodafone Data Traveller should be automatically enabled for Prepaid Vodafone sim, contract users need to call them to opt in. Best to check first in either case.
"To opt in, call us on 40062 from your Vodafone mobile phone. Or if you’re abroad, call us on +44 (0) 3333 040 012 from any phone."
"As a pay as you go customer you’ll automatically benefit from Vodafone Data Traveller and pay just £2 a day for each day you use it."
Using the internet abroad - it's easy on Vodafone