My name is Alex Hughes.
The court cannot deal with this hearinf in your absence; the solicitor cannot enter the plea on your behalf either.
How long are you planning to be abroad?
Yes. If you have a pre-booked and pre-paid holiday you can ask for an adjournment. You should give the tickets or itinerary to your solicitor to send to the court. Getting an adjournment in these circumstances is usually granted.
The court could decide that a delay wouldn't be 'in the interests if justice'. But to be honest with you I've not known them to refuse applications when a holiday has been booked and paid in advance. So long as you get your paperwork in asap you should be OK.