Look for one with 512MB of RAM, Centrino, Sempron or Turion. IGP gfx. £550 can you get a good specced laptop, probably too good if it's just for browsing. £400
ie this one
SiSM760GX
Acer 3004 range £430
AMD Sempron 3100+ - As powerful as P4 2.8GHz, 15% faster than 3000+
512MB DDR SDRAM
60GB Hard Drive
DVD Dual Layer Drive
15.4" WXGA Widescreen TFT Screen
or this for £440
Acer Aspire 1642ZWLMi
Intel Pentium-M Centrino 735A Processor 1.7 GHz
512 MB DDRII-533MHz SDRAM
60 GB Hard Drive
DVD Dual Layer Drive
15.4" WXGA Widescreen TFT Screen with CrystalBrite Technology
Intel 915GM 3D 128 MB shared graphics
£560 gets you this
Aspire 5102WLMi
Mobile AMD 64 Turion X2 TL50 1.6GHz
15.4" WXGA Acer CrystalBrite™ TFT LCD Display
100GB Serial ATA Hard Disk Drive
1024MB DDR II RAM
DVD-Super Multi Drive
ATI Radeon® Xpress 1100 integrated 3D graphics with up to 256MB of shared memory