ALLIANCE & Leicester and Bristol & West building societies are launching five-year Stock Exchange-linked bonds. Alliance & Leicester promises the full rise in the FT-SE 100 Index or 20 per cent gross interest, whichever is higher. The minimum investment is pounds 1,000. Bristol & West's bond pays 130 per cent gross of the index, and offers some protection against falls in the last three months. The original investment will always be returned. The minimum investment is pounds 5,000.