Well, I've come up with a suggestion which will give you 21 nights in Spain, for 2 people, for a total of �774.08. This includes all flights (inclusive of taxes, etc) and accommodation but excludes food and transfers.
Here's how I'd do it:
Fly out on Thursday, 15th December leaving Inverness at 1210. Arrive Bristol at 1340. (Total fares, for 2, = �25.98).
Fly from Bristol at 1820. Arrive Alicante 2145. (Total fares, for 2, = �49.98)
Stay 21 nights at Aguamarina self-catering apartments in Calpe (45 miles from Alicante airport). (Total price, for 2, = �433).
Fly back from Alicante on Thursday, 5th January at 1020. Arrive at Gatwick at 1155. (Total fares, for 2, = �125.14).
Leave Gatwick at 1405. Arrive Inverness 1550. (Total fares, for 2, = �39.98)
I don't know Calpe but it looks as if it might be a reasonable sort of place to use a a base for exploring the area. (Check this link:
http://www.inmocostablanca.com/calpe-spain.htm).
The biggest problem you might have with these suggestions is with your transfers to and from the airport. If you're hiring a car, with collection at the airport, you'll obviously have no problems. Otherwise you might want to select accommodation nearer to the airport (possibly in Alicante itself) to reduce transfer costs.
All of the above flights and accommodation are with Easyjet (www.easyjet.com) and, of course, prices are subject to fluctuation.
While I don't really expect you to follow my exact suggestions, I hope that I might have given you some ideas which will prove useful.
Chris