There are quite a number of cheap flights from the UK to Venice Marco Polo Airport, operated by various airlines. (There are also cheap flights to Venice Treviso Airport, which is a completely different airport - see how to get from Treviso to Croatia.)

One option in travelling from Venice would be to take one of the numerous daily trains from Venice Santa Lucia or Mestre stations to Trieste and then change there for more transportation options to Croatia. See Trenitalia for train timetables.

Catamaran Service from Venice to Istria
Venezia Lines operate routes from Venice to various Istrian ports (Porec, Rovinj, Pula, Rabac) as well as services to the island of Mali Losinj. Most services operate between June and September; more popular ones operate from May to October (e.g. Venice - Porec). Book online using the form below:

Venice - Pula by Bus
There is a daily service from Venice to Pula in summer which is run by Italian company Eurolines.

Flights from the UK to Venice Marco Polo
British Airways Flights from London Heathrow and London Gatwick
Easyjet Flights from London Gatwick, Bristol and East Midlands
Jet2.com Flights from Leeds Bradford, Manchester and Edinburgh
Thomsonfly Flights from London Gatwick and Manchester
flyThomasCook Flights from London Gatwick and Manchester

(N.B. Not all of the above flights operate all year round.)

Can I travel from Venice to Split or Dubrovnik by ferry?
It's a question we get asked quite frequently but, unfortunately, no - there are no ferries from Venice to either Split or Dubrovnik. Aside from the catamaran services to Istria and Mali Losinj (mentioned above), there is no ferry service from Venice to anywhere else Croatia.

Useful Travel Links
Venice Airport Information on getting to/from the airport
Trenitalia Train timetables for journeys within Italy
Die Bahn European train timetables