The only realistic way the Conservatives would have got a majority in 2010 (and likewise at future elections) is by hoovering up the rightist white working class vote which instead went UKIP/EDP/BNP.
I disagree with that, and to me the scenario sounds a little like wishful thinking. The combined UKIP/BNP voteshare in 2010 was only 5%, remember, and I don't see Cameron realistically being able to get much of that, no matter how hard he tried. These are the people who generally rejected the Conservative offering in 2005 and 2001 as well, after all.
A majority in 2010 was always (with hindsight) very unlikely, because of the sheer size of the electoral mountain the Tories had to climb. That said, the way to do it, in my view, is to butterfly "Cleggmania", and the idea in the minds of the public that there was an alternate way of kicking Labour without having to vote Conservative. Despite what UKIP may claim, the Lib Dems were an infinitely greater spoiler to the Conservatives than UKIP were in 2010.
So, no Cleggmania means the LDs and squeezed from their 2005 success, and the question is increasingly asked "why vote for this irrelevant party?" This is asked at every election, of course, but ITTL, Clegg's not able to provide a convincing answer in the form of his debate performance. You don't need to knock down the LD voteshare dramatically from its 2005 result to achieve this: say take the Lib Dems down to maybe 18% of the vote, with the majority of their 2010 converts voting Conservative. The end result would be something like
40/
31/
18, with the effect that the Conservatives are able to take maybe a dozen seats from the Lib Dems, and 15-20 more from Labour. The party now has 335 or so seats, a small but just about workable majority of about 20.
As for changes: obviously there's not going to be an AV referendum ITTL, and no moves to Lords Reform, although the shrinking of the House of Commons will go ahead. The lack of a crushing defeat for AV may very well mean it becomes part of Labour's electoral platform quite early on in the TL, which will obviously be quite a big change for the alternate 2015 election. The Lib Dems and Labour will, obviously, remain closer than IOTL.
As for the Government, I'm not sure the changes will be too radical. The Beecroft recommendations will probably largely be passed wholesale, and there may be marginally more aggressive attempts to regain powers from the EU early. Cameron's still unlikely to be bounced into offering a referendum until late 2012/early 2013, although here we might well see the referendum date being set sometime before the 2014/5 election, or even on the same date as the General Election. Speaking of GEs, there's not going to be a fixed term Parliament act.
The top rate of tax could be cut to 40%, but a part of me suspects Osborne will still go for 45% so he can claim that it is higher under the Conservatives than Labour. I reckon the Tories will probably steal the LD policy on personal allowances, but perhaps not pursue it as aggressively as the LDs have. There'd probably be a greater presentational focus on cheap energy, rather than green energy, so the progress of fracking developments will probably move maybe six months quicker ITTL. Transport investment I see largely going ahead as OTL, same for gay marriage. Cameron's still likely to try to outflank Salmond by bouncing him into a pre-2015 Scottish independence referendum: incidentally, a Conservative majority Government might well have two or three Scottish seats, rather than just one.
It'd be an interesting TL to see, I think. If only I could write political timelines!