I wrote a while ago about trying to arrange a trip to Sweden to ski ... without any direct flights, it wasn't easy to arrange, and so I never went !
Now that Easyjet have announced a weekly flight on a Sunday from LGW to OSD (which is about 80km from the ski area), it should make the trip more feasible.
The EZY flight departs LGW at 07:00, arriving OSD at 10:50 - and then departing at 11:10, arriving back into LGW at 12:55
The LGW-OSD price during March is between 42 gpb and 75 gbp for a single.
The OSD-LGW price during March is 27.50 gbp (26th), 33.50 gbp (19th) or 55 gbp (12th)
Getting to OSD on connecting flights from London takes a while - using SAS flights connecting in Stockholm, you could depart LHR at 10:35 and arrive OSD at 16:35 with a very safe 4 hour margin in ARN. Prices in March are about 88 gbp single.
It would be possible to get a shared transfer for these flights for 295 SEK each way per person (approx 27 gbp each way).
The same company also does shared transfers from Trondheim - at 13:15 and 17:15 on a Thursday (and further times on a Sunday) - but sadly the only direct flight from London to TRD arrives into TRD at 23:35 on a Thursday. The cost is 390 SEK per person each way.
However, there's a direct flight from TRD to LGW departing at 18:00 which would require getting the 13:30 bus from the ski resort (arriving at the airport around 16:00) - but it would be another option.
Another option would be to fly from London to Stockholm on Wednesday evening - so able to do a full day's work, and then travel up to Åre on Thursday morning. This might work better, as it appears the standard "handover" days in Åre are Thursday and Sunday. Flights are generally available for 52 gbp from LGW to ARN with Norwegian.
Flights from ARN to OSD are generally available for 54 gbp - with 5 flights a day from SAS and more from BRA (which are slightly more expensive).
Another option is the overnight train from Stockholm - a seat would cost 595 SEK and a berth would cost 746 SEK (68 gbp). The day time train takes about 7 hours and costs anything from 195 SEK, with a more typical price being 365 SEK (33 gbp). Prices are only currently available on the Swedish Rail website until 19th March - presumably because it's too far in advance.
As far as accommodation - it looks like there are basic self catering apartment/studios available near the main town for 268 eur for Thu-Sun - which sleep 2 or 3 people.
Wed 22nd eve LGW-ARN 52 gbp
Wed 22nd overnight train to Åre with cabin 68 gbp
Thu 23rd train to ski area 10 gbp
3 nights accomm 120 gbp (two people sharing the cheap accommodation)
3 days ski pass 114 gbp
3 days ski / boot hire 85 gbp
Sun 26th transfer to OSD airport 27 gbp
Sun 26th OSD-LGW 17.50 gbp
Total 493.50 plus transfer to and from LGW