The official stance from Vodafone UK is to text the word "WEB" to 40127 and they will send you the right settings.

There are two connections: wap:wap@wap.vodafone.co.uk and web:web@internet (user:passwd@apn). The wap connection is (apparently) considered by Vodafone to be legacy but some apps still use WAP and internet connections should also work with WAP. The question remains - are there any Sailfish apps that need WAP?