Where have you been? What have you seen?
Essentially yes. You can file a flight plan here. You need to apply for an account, which is free for personal use but you need to be a qualified pilot and have a CAA reference number in order to get the account. There are third parties that have different web interfaces that make the whole process much easier but you have to pay a fee.

My understanding is that if the flight plan is for a VFR flight, then it goes straight into the system. If it's for an IFR flight in controlled airspace, there is an approval process - the routing must be approved by the controlling authority.