Our portfolio system takes the quoted price to be per individual instrument. However, in some cases, bonds (and selected preference shares) are quoted as trading in a block of 100.
A stock will typically trade in pence (i.e minor currency units), denoted by "currency = GBX" on the LSE website (for example, Atkins). However, many bonds trade in GBP (i.e. major currency units) reflecting a block of 100 bonds. An example of this is Bradford & Bingley's BBN where the GBP price quoted is per GBP100 nominal of bonds purchased.
In such cases, to make the valuation work within the portfolio system, you will need to reduce the quantity you hold by a factor of 100. We hope to automate this in due course.