My advice is to try and buy a front end as complete as possible as it tends to end up costing more money when you buy each bit seperatly.
Its also worth keeping an eye on the american ebay site as parts over there are generally mucho cheapo then over here. Stuff usually sells for $ for what it costs in £ here and with the favourable exchange rate it often works out cheaper. Got to be careful to factor the shipping prices in to and i'm not certain on what happens with import charges on 2cnd hand parts.
just a quick scan here's a load of bits in a oner
Yet another edited link
i got most of my stuff from the states without paying any import costs.