Ryanair is the only airline which flies direct from Dublin Airport to Seville Airport. You are unlikely to find a cheaper rate however it’s still worth your while having a look at some price comparison sites such as ebookers or Opodo. It’s a long shot though.
You can get flights from London Gatwick and London Stansted direct to Seville Airport. Clickair offers a direct flight from Gatwick while again it’s Ryanair who offer a direct flight from Stansted.
Elsewhere in the UK you can fly direct from Liverpool Airport to Seville. In Europe Ryanair offers the following direct flights to Seville:
• Cagliari to Seville
• Barcelona to Seville
• Dusseldorf to Seville
• Frankfurt to Seville
• Milan to Seville
• Pisa to Seville
At certain times of the year it may work out cheaper to get a flight to Malaga or Madrid and then travel to Seville from there. As you can see Ryanair is very much the main airline when looking for a flight from the UK or Ireland to Seville.
If you don’t mind the inconvenience you may be able to find some cheaper connecting routes from other airport within the UK.