Satellite group Inmarsat headed the fallers on the FTSE 250 on Monday after a government agency highlighted potential GPS-interference issues in its partner's (LightSquared) high-speed wireless network in the US.Inmarsat became involved with LightSquared in August 2010, when it agreed a plan "to enable the re-banding and efficient reuse of L-band radio spectrum covering North America." In 2010, the Cooperation Agreement provided Inmarsat with $121.2m in revenue. Travel group TUI Travel was on the rise after UBS added the firm to its 'M&A Watch List' and initiated coverage with a buy rating and 220p target, a significant upside to Friday's closing price of 161.7p. UBS said that TUI has a more developed product mix to sector peer Thomas Cook, with a better exposure to growth. The broker said: "We also expect the stock to receive support from a potential takeover by TUI AG", the firm's German parent company.House builder Bovis Homes rose after saying that pre-tax profits for 2011 will be in line with market consensus. The group also said it is well positioned to improve returns in 2012 and beyond.Oil and gas group Exillon Energy fell despite saying that the average daily production reached 11,055 barrels for the month of December, up from November's 10,935 barrels a day. Retailers Home Retail, Dixons and SuperGroup were also among the high risers of the day.BCFTSE 250 - RisersPerform Group (PER) 234.80p +6.73%Afren (AFR) 114.50p +3.62%Home Retail Group (HOME) 87.90p +3.41%Supergroup (SGP) 584.50p +3.27%TUI Travel (TT.) 166.00p +2.66%Dixons Retail (DXNS) 9.94p +2.58%Cape (CIU) 385.50p +2.53%Spirit Pub Company (SPRT) 44.50p +2.30%BBA Aviation (BBA) 187.40p +2.24%Talvivaara Mining Company (TALV) 303.10p +1.99%FTSE 250 - FallersInmarsat (ISAT) 393.80p -6.24%Regus (RGU) 86.65p -3.72%Heritage Oil (HOIL) 177.30p -2.64%Halfords Group (HFD) 296.90p -2.53%Anglo Pacific Group (APF) 268.50p -2.36%Northgate (NTG) 207.00p -2.36%Berendsen (BRSN) 420.30p -2.07%EnQuest (ENQ) 104.60p -1.97%Brewin Dolphin Holdings (BRW) 142.40p -1.93%Spectris (SXS) 1,454.00p -1.89%