Interest rates vary between societies, sometimes substantially. Some of the smaller ones offer premium rates to attract investors.
It is not always easy to find out what is available, or to determine whether, say, the five- branch Haywards Heath & District Building Society has the edge on the giant Halifax.
Kathryn Deane, who edits the monthly newsletter Building Society Choice, says that savers tend to watch interest rates more closely when they are rising. 'However, there is a good argument that people need information more when rates are falling,' she says.
Building Society Choice produces a monthly listing of the best building society rates on offer, categorised by length of notice period and the minimum investment needed.
The publication, available only by annual subscription (currently pounds 12), is modelled on the Which? magazine concept of identifying the best buy.
A typical comment in the latest issue advises readers: 'Go for instant access and mop up on the postal bargains there . . . and, for once, take a serious look at fixed-rate bonds.'
According to Kathryn Deane, most subscribers are individual investors. In contrast, MoneyFacts (or, as it prefers, Money pounds acts) magazine markets itself primarily to financial advisers and other professionals, though its publisher, John Woods, says individuals are among its subscribers.
MoneyFacts offers a comprehensive monthly listing of the interest rates being paid on each of the investment products of about 70 building societies. It also includes full details on bank accounts, credit cards, mortgage rates, Tessas, and National Savings.
MoneyFacts and Building Society Choice suffer from the limitations of monthly publication, especially when interest rates are moving fast. The best buys identified by Building Society Choice frequently change markedly between issues.
Ms Deane says she does not expect investors necessarily to shift their money between accounts each month. 'We expect subscribers to look at the pattern over a period of months. A rate that stays in our tables for several months is likely to be more appealing than one that drops in and out.'
There is also the question of ensuring that information is accurate. This is not helped, according to Ms Deane, by the fact that building society staff are not always properly informed of what their own society is offering.
She and John Woods say their publications make strenuous efforts to check their information. 'One hundred per cent accuracy is impossible, but it's a bad month if we have much in the way of mistakes. We physically ring and check with all the institutions we list,' Mr Woods says.
MoneyFacts recently increased its size to 32 pages a month, at the same time increasing its annual subscription from pounds 22.50 to pounds 32.50. Single complimentary copies are sent on request. In contrast, would- be subscribers to Building Society Choice must pay their money first, though there is a partial money-back arrangement for those who wish to cancel within the first three months. A combined annual subscription of pounds 29 brings copies of three companion newsletters, covering bank accounts, Tessas and offshore investments.
Information on current building society rates can also be obtained from other sources. Chase de Vere Investments, for example, updates its rates tables on a daily basis. These list the best rates on offer for instant access and notice accounts, and also the best accounts offering monthly interest. Chase de Vere provides individual copies of its tables free on request.
Details from Building Society Choice, MoneyGuides, Rattlesden, Bury St Edmunds IP30 0SF (0449 736287); MoneyFacts, Walshams House, Stalham, Norwich NR12 9AH (0692 582103); Chase de Vere Investments, 63 Lincoln's Inn Fields, London WC2A 3JX (071-404 5766 or via operator to Freephone Chase de Vere).