It will cost you another 50% (of the home version cost) for the pro version and in fact you system will actually be easier to maintain especially using security. The big problem is that if you require XP pro and have XP home (in the UK) you will have to by the full retail version and even worse the home version you have cannot then be used by another person or even on another machine, in other words the cost of XP Home will be lost. This is madness. In effect whilst the upgrade will be successful you will have paid twice for the same operating system.
Are there really different rules in different countries? According to Microsoft XP home qualifies for an upgrade to XP Pro. In case you buy a full retail version of XP, you can of course install the other version on another computer or sell it, if it isn't a OEM version that was bundled with hardware.
Bluzeboy, check whether you really need the (few) extra features of Pro and whether they are worth the money.