In the UK, Parcelforce have just terminated the Parcelforce Standard
Tariff. Previously a parcel weighing 4Kg cost £6.50 to post in the UK.
Now it costs £11.85 with Parcelforce 48. Is there a cheaper way to
send a parcel of this weight from one UK address to another? If so
what is the cost and the name of the carrier?

Hello steveuk-ga,
If you switch to Royal Mail (Consignia) you will find a 4kg package
sent from London W1 to Glasgow G44 sent via Royal Mail Standard
Parcels delivery aim 3 day service costs £6.55 (no proof of delivery
or compensation value) according to their online price calculator

( http://www.consignia-online.com/portal/default/all/home?paf_gear_id=100003&paf_gm=content&paf_dm=full&servicesGuideConsigniaPage=servicesGuideUKSendingInfo
)
"Royal Mail Standard Parcels

This service delivers to all UK destinations normally within three to
five working days after posting. Parcels up to 30kg in weight may be
sent using this service with a maximum dimension of length 1.5 metres.
The length and girth of the parcel combined must not exceed 3 metres.
Compensation 
Compensation up to £20 per parcel for loss or damage is included in
the price. Enhanced compensation up to £500 per parcel is available
for an additional fee. Our compensation scheme does not cover certain
items. For further details please call us on 0845 7740 740. If you are
Deaf or hard of hearing then please call our Textphone service on 0845
600 0606 (all calls are charged at local rate). "
source: http://www.consignia-online.com/servicesGuide/contentPopup.jhtml?serviceRef=432F1A94-F45F-4586-B1B4-0E80FBD06795
Prohibitions and restrictions on this page (
http://www.consignia-online.com/portal/default/all/home?paf_gear_id=100002&paf_gm=content&paf_dm=full&paf_gear_state=con_content&xmlPath=/docContent/xml/applicationContent/servicesGuide/sg505ProhibRestrict.xml&backButtonDisplay=true&isContent=true
)
I hope that helps, if you need clarification let me know,
kind regards lot-ga

Well answered, good detail.