According to the HMRC if you work at home voluntarily you cannot claim any tax relief. However since in your case this is compulsory you should be able to claim tax relief.
Tax relief will only be given to costs which are deemed to be wholly, exclusively and necessarily for your work. For example business phone calls or the extra cost of gas and electricity for your work area. You cannot claim for expenses that you use for both private and business use, for example, rent or broadband access.
An additional approach if offered by the HMRC, where your employer can pay you up to £4 a week (£18 a month) to cover your additional costs if you have to work from home.