1. I got the CGT letting relief here:
http://www.hmrc.gov.u...y/sell-own-home.htm#4
The maximum amount is £40K, but the calculation is obviously complex!
2. Stamp Duty Land Tax rates are here:
http://www.hmrc.gov.u...ates-thresholds.htm#1
If your son is a first time buyer, or if you are in a disadvantaged area, then there is no duty on a £150K house at present. Otherwise the duty is payable.
3. If your son owns the house & lives in it as his only or principal residence then there will be no CGT when he sells it.
4. There should be some CGT relief as you lived in the house for a while, but I've no idea how it is worked out.
5. If you give the house to your son (instead of selling it) you will have to pay CGT.