Hi, first of all. Is the upload, download speed you stated the one given to you by your isp? as you never get the full speeds as described to you by the provider, its always some what slower.

Also, i use core ftp myself & its not the best ftp software, but its simple & smart & thats how i like it. However, when uploading, core ftp does crash if your uploading lots of images, files n so forth in one go. Try uploading in batches to reduce the ammount of files it has to seek threw before uploading.

Also, the average upload speed in the UK are about 20-40kbps unless u go business class then it gets much better for high cost.