Thanks for your reply.
The slower spin speeds seems to be happening on every wash now, so i do not think that it is the load not being balanced properly. There is also no grating sound or any abnormal sounds coming from my machine. It just seems that the spin speed is much slower than before and therefore not drying my clothes properly.
I have taken the top off the washing machine to have a look at the belt and it does not look slack and it is difficult to try and pull the belt of the spindle on the motor. I have had the motor and the brushes changed about 9 months ago at a cost of over £100.
I rang around the local washing machine repairmen in my area and they want at least £30 just to come and have a look. Im not sure what the problem could be, or if it is worth having someone to come and try and repair the machine, or just go out and buy a new model. This is an old machine nowadays and i don't know how it compares with the modern machines, so the dilemma is should i just call it a day and buy a new one, or do you think i should get it looked at and hope it can be repaired cost effectivly.