I'll break this into two parts: electronics hobbyist, and not. Not surprisingly, there are more options for the former. As part of the BAR898HG I think you already have a wireless outdoor sensor (THGR228N ?).
If you are an electronics hobbyist (or want to learn) you can keep the outdoor sensor you already have and build a receiver for it that will interface to your PC. If you have lots of free time on your hands and like projects this might be a fit -- otherwise skip this paragraph and read on. I'll also warn you ahead of time that I'm partial to the WSDL data logging program (which does not have a huge following). On the up side however, you can build a receiver for the existing sensor with an Arduino mini-computer board and a "WxShield" which is explained at
http://www.osengr.org. The total cost would be well under your limit. The WSDL program can then accept input from the Arduino unit over USB and will perform data logging and display of the data. I even have a blank PC board for the version 1 shield I might be willing to send you for the price of postage (from the US) -- PM me on this site if interested. One advantage to this approach is that you can receive data from all Oregon Scientific version 2.1 and 3.0 sensors and can add more of these over time as you see fit. A nice expansion path is to purchase the WMR80 unit. This unit does not offer comptuer connectivity and is usually around $100US -- and you get the anemometer, rain gauge and one more temp/RH sensor in the bargain. All of the sensors will operate with your wireless receiver plus you can still use the console around the house as well.
If you're not (or don't want to be) an electronics hobbyist, then there are still some interesting options through Oregon Scientific, but you wont' be able to use the existing THGR228N sensor. The least expensive option would be the WMR88 which I think might fit within your budget (not sure on the exchange rates however). Check OS UK web site for your price. The WMR100 is probably not within your desired price range; the known differences are that the WMR88 reports wind data less frequently (every 60 seconds versus 15 seconds for the WMR100) although the wireless sensors are identical. Not sure how many wireless sensors the WMR88 supports, but the WMR100 supports up to ten. You must use the version 3 sensors with this unit which are rather pricey compared to the version 2.1 sensors (used by your BAR898) -- although as far as I can tell (and I've done a lot of work and research with these units) they are both just as accurate. With the OS option I think you have a choice of several different data logging software programs -- both free and pay-for. Please double-check on support for the WMR88 with the different programs. Also, the OS consoles are sometimes a little finicky about receiving the outdoor sensors over the advertised distances; very difficult to predict what performance you'll see there. Placing outdoor sensors so they are line-of-site through no more than one building wall is a good strategy.
Anyway -- thats the Oregon Scientific picture; as DanS points out there are other options and not just those he mentions. I freely admit that my inputs are biased and you should take them with a grain of salt (or two)!