By Jennifer Hill, Personal Finance Correspondent

LONDON (Reuters) - It is a conundrum facing millions with a mortgage -- to fix or track?

Some 1.4 million borrowers will see their existing fixed rates expire this year, according to the Council of Mortgage Lenders (CML).

That figure, say others, is in reality far higher -- and could hit something approaching four million when you include people coming to the end of deals like tracker and discounted rates.

Ray Boulger, for example, senior technical manager at independent mortgage broker John Charcol, estimates that 3.6 million people will come to the end of the offer period on their home loan this year.

Rates, although still historically low, are higher now than they were two or three years ago: those coming off cheap fixed-rate deals will be hit with at least 1 percent more.

Homeowners are set for a "rate shock" that will add an average 210 pounds to their monthly mortgage bills if they move onto their lender's standard variable rate (SVR).

"The figure for two-year fixed rates was used primarily to talk about 'payment shock', but there will just as much -- and in some cases more -- payment shock for people coming off a good tracker or discount, and often also for people coming off some longer-term fixed rates," says Boulger.

"For example, in mid-2003 several lenders offered five-year fixed rates below 4 percent."