I currently use an excel spreadsheet that I record my time at
different clients and what I did there etc, then at the end of the
month I use that data as a reminder of what I need to invoice for.

It works OK but to take things to the next level of efficiency I am
wondering if I need something that is web-based ... mainly because I
don't always have access to my excel sheet when clients call. However
I am invariably internet-connected as generally speaking I have to be
in order to help with their problem. So, I was thinking I need
something on my private web site that I can log in to, put start and
end times, choose the client, write a one line description of what I
did, etc. Or, should I just be carrying a good old fashioned paper
notepad around at all times, and transferring the data to my proper
billing records once a night or once a week.

Some clients I bill per 15minutes, most per hour, some per day, and
some have a fixed amount of "free" support time per month (I'm on a
retainer deal) but I need to know when their usage of me exceeds a
certain time threshold.

I can write something myself but before I do, was just wondering if my
fellow consultants already knew of something that exists already to
save me the time. Ideally needs to be free or less than £100. So what
do people do about recording the time they spend on each client?

A bonus would be if the system also tracked expenses, for instance the
tube fare to get to the client, or sometimes they call and ask me to
bring something in so I stop off at PC World on the way to get it for
them, it would be nice to make a note of those expenses as I go
instead of trying to remember everything at the end of the day or
week.