Hi Maryanne --- Do not be pressurised into taking out further debt you can't afford to appease your existing creditors, it is neither beneficial to you or in your interests to incur further debt to service an existing debt, assuming you would even be offered it. !
At the very least if you have contacted them with a reasonable offer then should this end in the courts at a later date, you will at least be seen to have acted reasonably and responsibly, in offering to pay what you could afford at the time.
You need to re-submit your offer of £150 per week in writing with a full expenditure sheet, showing your income and expenses and send them by recorded delivery this time. Should they still refuse to accept your offer at least you can prove to a court that you sent an offer and did try everything possible within your control to re-pay the arrears.