You seem overly concerned about the weight (especially when discussing steel frames)
If frame weight is a major factor and you are after steel then you may need to allocate more of the £1200 towards the frame. That wouldn't be abnormal as the ratio you are putting towards the frame is on the low side currently. Most people putting together a £1200 bike would spend more than £250 on the frame.
You seem overly concerned about the weight (especially when discussing steel frames)
If frame weight is a major factor and you are after steel then you may need to allocate more of the £1200 towards the frame. That wouldn't be abnormal as the ratio you are putting towards the frame is on the low side currently. Most people putting together a £1200 bike would spend more than £250 on the frame.