Hello I am a lawyer with over 15 years experience I will try to help you with this.
Have you been charged yet or are you on police bail without being charged yet. I assume you have been arrested for possession with intent to supply and that the police say that the money is the proceeds of crime. If you can confirm this is right I will answer your question.
The sentencing guidelines re: possession of drugs with intent to supply can be found at this link.
http://sentencingcouncil.judiciary.gov.uk/docs/Drug_Offences_Definitive_Guideline_final_(web).pdf you shuold look at p10 and the tables on subsequent pages.
These are guidelines for sentencing people who are found guilty after a trial and who have no previous convictions. If you plead guilty the sentence will be reduced by up to a third. The sooner you plead the greater the reduction.
1 oz = 28.35 grams. This will put you in the lowest category of seriousness (Cat 4 in the table) This category goes up to 100g so you are towards the bottom of the range. On the assumption that you would be sentenced as having a lesser role. (look at page 11 to see where you think your involvement fits) the sentence would be in the the range of High level community order - 3 years imprisonment with a starting point of 18 months. This will be reduced to take account of the relatively low weight, if you plead GuIlty there will be a further reduction. The precise sentence will depend on the facts of the case and your personal mitigation. However if you come to be sentenced for possession a class A drug with intent to supply it is very likely that a prison sentence will be imposed. Assuming that your are considered to have a lesser role and there are no aggravating features then I think a sentence of about 6-8 months is likely. There will be an outside chance of a suspended sentence. This answer is for an early guilty plea, if found guilty after trial imprisonment for 9-12 months would be likely in a lesser role case.
It may be that your case is that you were in possession but that it was for your own use. If you are sentenced for simple possession then you should look at p 31 of the guideline and you will see that the range is a fine to a year’s custody. As a first time offender, admitting possession at an early stage custody is unlikely but for quite a large amount for simple possession it is likely you will get a fairly stiff community order.
Ordinarily a prisoner serves half of the sentence in prison and half on licence in the community.
I hope this answer is helpful but please bear in mind that I am answering with limited information. If you have any follow up questions please feel free to ask